String.Join 方法

定义

连接指定数组的元素或集合的成员,在每个元素或成员之间使用指定的分隔符。Concatenates the elements of a specified array or the members of a collection, using the specified separator between each element or member.

重载

Join(Char, Object[])

连接对象数组的字符串表示形式,其中在每个成员之间使用指定的分隔符。Concatenates the string representations of an array of objects, using the specified separator between each member.

Join(Char, String[])

连接字符串数组,其中在每个成员之间使用指定的分隔符。Concatenates an array of strings, using the specified separator between each member.

Join(String, IEnumerable<String>)

串联类型为 IEnumerable<T>String 构造集合的成员,其中在每个成员之间使用指定的分隔符。Concatenates the members of a constructed IEnumerable<T> collection of type String, using the specified separator between each member.

Join(String, Object[])

串联对象数组的各个元素,其中在每个元素之间使用指定的分隔符。Concatenates the elements of an object array, using the specified separator between each element.

Join(String, String[])

串联字符串数组的所有元素,其中在每个元素之间使用指定的分隔符。Concatenates all the elements of a string array, using the specified separator between each element.

Join(Char, String[], Int32, Int32)

连接字符串数组,其中在每个成员之间使用指定的分隔符,并且从位于 startIndex 位置的 value 中的元素开始,并连接多达 count 个元素。Concatenates an array of strings, using the specified separator between each member, starting with the element in value located at the startIndex position, and concatenating up to count elements.

Join(String, String[], Int32, Int32)

串联字符串数组的指定元素,其中在每个元素之间使用指定的分隔符。Concatenates the specified elements of a string array, using the specified separator between each element.

Join<T>(Char, IEnumerable<T>)

串联集合的成员,其中在每个成员之间使用指定的分隔符。Concatenates the members of a collection, using the specified separator between each member.

Join<T>(String, IEnumerable<T>)

串联集合的成员,其中在每个成员之间使用指定的分隔符。Concatenates the members of a collection, using the specified separator between each member.

Join(Char, Object[])

连接对象数组的字符串表示形式,其中在每个成员之间使用指定的分隔符。Concatenates the string representations of an array of objects, using the specified separator between each member.

public:
 static System::String ^ Join(char separator, ... cli::array <System::Object ^> ^ values);
public static string Join (char separator, params object[] values);
static member Join : char * obj[] -> string
Public Shared Function Join (separator As Char, ParamArray values As Object()) As String

参数

separator
Char

要用作分隔符的字符。The character to use as a separator. 只有在 separator 具有多个元素时,value 才包括在返回的字符串中。separator is included in the returned string only if value has more than one element.

values
Object[]

将连接其字符串表示形式的对象数组。An array of objects whose string representations will be concatenated.

返回

一个由 values 的元素组成的字符串,这些元素以 separator 字符分隔。A string that consists of the elements of values delimited by the separator character.

-or-

如果 values 包含零个元素或 values 的所有元素都为 null,则为 EmptyEmpty if values has zero elements or all the elements of values are null.

异常

valuenullvalue is null.

生成的字符串长度超出了允许的最大长度 (MaxValue)。The length of the resulting string overflows the maximum allowed length (MaxValue).

Join(Char, String[])

连接字符串数组,其中在每个成员之间使用指定的分隔符。Concatenates an array of strings, using the specified separator between each member.

public:
 static System::String ^ Join(char separator, ... cli::array <System::String ^> ^ value);
public static string Join (char separator, params string[] value);
static member Join : char * string[] -> string
Public Shared Function Join (separator As Char, ParamArray value As String()) As String

参数

separator
Char

要用作分隔符的字符。The character to use as a separator. 只有在 separator 具有多个元素时,value 才包括在返回的字符串中。separator is included in the returned string only if value has more than one element.

value
String[]

要连接的字符串数组。An array of strings to concatenate.

返回

一个由 value 的元素组成的字符串,这些元素以 separator 字符分隔。A string that consists of the elements of value delimited by the separator character.

-or-

如果 value 包含零个元素或 value 的所有元素都为 null,则为 EmptyEmpty if value has zero elements or all the elements of value are null.

异常

valuenullvalue is null.

生成的字符串长度超出了允许的最大长度 (MaxValue)。The length of the resulting string overflows the maximum allowed length (MaxValue).

Join(String, IEnumerable<String>)

串联类型为 IEnumerable<T>String 构造集合的成员,其中在每个成员之间使用指定的分隔符。Concatenates the members of a constructed IEnumerable<T> collection of type String, using the specified separator between each member.

public:
 static System::String ^ Join(System::String ^ separator, System::Collections::Generic::IEnumerable<System::String ^> ^ values);
[System.Runtime.InteropServices.ComVisible(false)]
public static string Join (string separator, System.Collections.Generic.IEnumerable<string> values);
static member Join : string * seq<string> -> string
Public Shared Function Join (separator As String, values As IEnumerable(Of String)) As String

参数

separator
String

要用作分隔符的字符串。separatorThe string to use as a separator.separator 包括在返回的字符串中(只有在 values 具有多个元素时)。is included in the returned string only if values has more than one element.

values
IEnumerable<String>

一个包含要串联的字符串的集合。A collection that contains the strings to concatenate.

返回

一个由 values 的成员组成的字符串,这些成员以 separator 字符串分隔。A string that consists of the members of values delimited by the separator string.

-or-

如果 values 包含零个元素或 values 的所有元素都为 null,则为 EmptyEmpty if values has zero elements or all the elements of values are null.

属性

异常

valuesnullvalues is null.

生成的字符串长度超出了允许的最大长度 (MaxValue)。The length of the resulting string overflows the maximum allowed length (MaxValue).

示例

下面的示例使用埃拉托色 of 尼斯筛法算法来计算小于或等于100的质数。The following example uses the Sieve of Eratosthenes algorithm to calculate the prime numbers that are less than or equal to 100. 它将结果分配给类型 StringList<T> 对象,然后将其传递给 Join(String, IEnumerable<String>) 方法。It assigns the result to a List<T> object of type String, which it then passes to the Join(String, IEnumerable<String>) method.

using System;
using System.Collections.Generic;

public class Example
{
   public static void Main()
   {
      int maxPrime = 100;
      List<int> primes = GetPrimes(maxPrime);
      Console.WriteLine("Primes less than {0}:", maxPrime);
      Console.WriteLine("   {0}", String.Join(" ", primes));
   }

   private static List<int> GetPrimes(int maxPrime)
   {
      Array values = Array.CreateInstance(typeof(int), 
                              new int[] { maxPrime - 1}, new int[] { 2 });
      // Use Sieve of Eratosthenes to determine prime numbers.
      for (int ctr = values.GetLowerBound(0); ctr <= (int) Math.Ceiling(Math.Sqrt(values.GetUpperBound(0))); ctr++)
      {
                           
         if ((int) values.GetValue(ctr) == 1) continue;
         
         for (int multiplier = ctr; multiplier <=  maxPrime / 2; multiplier++)
            if (ctr * multiplier <= maxPrime)
               values.SetValue(1, ctr * multiplier);
      }      
      
      List<int> primes = new List<int>();
      for (int ctr = values.GetLowerBound(0); ctr <= values.GetUpperBound(0); ctr++)
         if ((int) values.GetValue(ctr) == 0) 
            primes.Add(ctr);
      return primes;
   }   
}
// The example displays the following output:
//    Primes less than 100:
//       2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97
Imports System.Collections.Generic

Module Example
   Public Sub Main()
      Dim maxPrime As Integer = 100
      Dim primes As List(Of String) = GetPrimes(maxPrime)
      Console.WriteLine("Primes less than {0}:", maxPrime)
      Console.WriteLine("   {0}", String.Join(" ", primes))
   End Sub
   
   Private Function GetPrimes(maxPrime As Integer) As List(Of String)
      Dim values As Array = Array.CreateInstance(GetType(Integer), _
                              New Integer() { maxPrime - 1}, New Integer(){ 2 }) 
        ' Use Sieve of Eratosthenes to determine prime numbers.
      For ctr As Integer = values.GetLowerBound(0) To _
                           CInt(Math.Ceiling(Math.Sqrt(values.GetUpperBound(0))))
         If CInt(values.GetValue(ctr)) = 1 Then Continue For
         
         For multiplier As Integer = ctr To maxPrime \ 2
            If ctr * multiplier <= maxPrime Then values.SetValue(1, ctr * multiplier)
         Next   
      Next      
      
      Dim primes As New List(Of String)
      For ctr As Integer = values.GetLowerBound(0) To values.GetUpperBound(0)
         If CInt(values.GetValue(ctr)) = 0 Then primes.Add(ctr.ToString())
      Next            
      Return primes
   End Function   
End Module
' The example displays the following output:
'    Primes less than 100:
'       2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97

注解

如果 null``separator,则改为使用空字符串(String.Empty)。If separator is null, an empty string (String.Empty) is used instead. 如果 null``values 的任何成员,则改为使用空字符串。If any member of values is null, an empty string is used instead.

Join(String, IEnumerable<String>) 是一种简便方法,使你可以连接 IEnumerable(Of String) 集合中的每个元素,而无需先将元素转换为字符串数组。Join(String, IEnumerable<String>) is a convenience method that lets you concatenate each element in an IEnumerable(Of String) collection without first converting the elements to a string array. 它对语言集成查询(LINQ)查询表达式特别有用。It is particularly useful with Language-Integrated Query (LINQ) query expressions. 下面的示例将包含字母表的大写或小写字母的 List(Of String) 对象传递到 lambda 表达式,该表达式选择等于或大于特定字母的字母(在本例中为 "M")。The following example passes a List(Of String) object that contains either the uppercase or lowercase letters of the alphabet to a lambda expression that selects letters that are equal to or greater than a particular letter (which, in the example, is "M"). Enumerable.Where 方法返回的 IEnumerable(Of String) 集合会传递到 Join(String, IEnumerable<String>) 方法,以单个字符串的形式显示结果。The IEnumerable(Of String) collection returned by the Enumerable.Where method is passed to the Join(String, IEnumerable<String>) method to display the result as a single string.

using System;
using System.Collections.Generic;
using System.Linq;

public class Example
{
   public static void Main()
   {
      string output = String.Join(" ", GetAlphabet(true).Where( letter => 
                      letter.CompareTo("M") >= 0));
      Console.WriteLine(output);  
   }

   private static List<string> GetAlphabet(bool upper)
   {
      List<string> alphabet = new List<string>();
      int charValue = upper ? 65 : 97;
      for (int ctr = 0; ctr <= 25; ctr++)
         alphabet.Add(Convert.ToChar(charValue + ctr).ToString());
      return alphabet; 
   }
}
// The example displays the following output:
//      M N O P Q R S T U V W X Y Z
Imports System.Collections.Generic
Imports System.Linq

Module modMain
   Public Sub Main()
      Dim output As String = String.Join(" ", GetAlphabet(True).Where(Function(letter) _
                                                         letter >= "M"))
        
      Console.WriteLine(output)                                     
   End Sub
   
   Private Function GetAlphabet(upper As Boolean) As List(Of String)
      Dim alphabet As New List(Of String)
      Dim charValue As Integer = CInt(IIf(upper, 65, 97))
      For ctr As Integer = 0 To 25
         alphabet.Add(ChrW(charValue + ctr).ToString())
      Next
      Return alphabet 
   End Function
End Module
' The example displays the following output:
'      M N O P Q R S T U V W X Y Z

另请参阅

Join(String, Object[])

串联对象数组的各个元素,其中在每个元素之间使用指定的分隔符。Concatenates the elements of an object array, using the specified separator between each element.

public:
 static System::String ^ Join(System::String ^ separator, ... cli::array <System::Object ^> ^ values);
[System.Runtime.InteropServices.ComVisible(false)]
public static string Join (string separator, params object[] values);
static member Join : string * obj[] -> string
Public Shared Function Join (separator As String, ParamArray values As Object()) As String

参数

separator
String

要用作分隔符的字符串。The string to use as a separator. 只有在 separator 具有多个元素时,values 才包括在返回的字符串中。separator is included in the returned string only if values has more than one element.

values
Object[]

一个数组,其中包含要连接的元素。An array that contains the elements to concatenate.

返回

一个由 values 的元素组成的字符串,这些元素以 separator 字符串分隔。A string that consists of the elements of values delimited by the separator string. 如果 values 为空数组,该方法将返回 EmptyIf values is an empty array, the method returns Empty.

属性

异常

valuesnullvalues is null.

生成的字符串长度超出了允许的最大长度 (MaxValue)。The length of the resulting string overflows the maximum allowed length (MaxValue).

示例

下面的示例使用埃拉托色 of 尼斯筛法算法来计算小于或等于100的质数。The following example uses the Sieve of Eratosthenes algorithm to calculate the prime numbers that are less than or equal to 100. 它将结果分配给一个整数数组,然后将结果传递给 Join(String, Object[]) 方法。It assigns the result to a integer array, which it then passes to the Join(String, Object[]) method.

using System;
using System.Collections.Generic;

public class Example
{
   public static void Main()
   {
      int maxPrime = 100;
      int[] primes = GetPrimes(maxPrime);
      Console.WriteLine("Primes less than {0}:", maxPrime);
      Console.WriteLine("   {0}", String.Join(" ", primes));
   }

   private static int[] GetPrimes(int maxPrime)
   {
      Array values = Array.CreateInstance(typeof(int), 
                              new int[] { maxPrime - 1}, new int[] { 2 }); 
      // Use Sieve of Eratosthenes to determine prime numbers.
      for (int ctr = values.GetLowerBound(0); ctr <= (int) Math.Ceiling(Math.Sqrt(values.GetUpperBound(0))); ctr++)
      {
                           
         if ((int) values.GetValue(ctr) == 1) continue;
         
         for (int multiplier = ctr; multiplier <=  maxPrime / 2; multiplier++)
            if (ctr * multiplier <= maxPrime)
               values.SetValue(1, ctr * multiplier);
      }      
      
      List<int> primes = new List<int>();
      for (int ctr = values.GetLowerBound(0); ctr <= values.GetUpperBound(0); ctr++)
         if ((int) values.GetValue(ctr) == 0) 
            primes.Add(ctr);
      return primes.ToArray();
   }   
}
// The example displays the following output:
//    Primes less than 100:
//       2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97
Module Example
   Public Sub Main()
      Dim maxPrime As Integer = 100
      Dim primes() As Integer = GetPrimes(maxPrime)
      Console.WriteLine("Primes less than {0}:", maxPrime)
      Console.WriteLine("   {0}", String.Join(" ", primes))
   End Sub
   
   Private Function GetPrimes(maxPrime As Integer) As Integer()
      Dim values As Array = Array.CreateInstance(GetType(Integer), _
                              New Integer() { maxPrime - 1}, New Integer(){ 2 }) 
        ' Use Sieve of Eratosthenes to determine prime numbers.
      For ctr As Integer = values.GetLowerBound(0) To _
                           CInt(Math.Ceiling(Math.Sqrt(values.GetUpperBound(0))))
         If CInt(values.GetValue(ctr)) = 1 Then Continue For
         
         For multiplier As Integer = ctr To maxPrime \ 2
            If ctr * multiplier <= maxPrime Then values.SetValue(1, ctr * multiplier)
         Next   
      Next      
      
      Dim primes As New System.Collections.Generic.List(Of Integer)
      For ctr As Integer = values.GetLowerBound(0) To values.GetUpperBound(0)
         If CInt(values.GetValue(ctr)) = 0 Then primes.Add(ctr)
      Next            
      Return primes.ToArray()
   End Function   
End Module
' The example displays the following output:
'    Primes less than 100:
'       2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97

注解

如果 separator null 或者第一个元素 values 之外的任何元素 null,则改用空字符串(String.Empty)。If separator is null or if any element of values other than the first element is null, an empty string (String.Empty) is used instead. 如果 null``values 的第一个元素,请参阅 "调用方的说明" 部分。See the Notes for Callers section if the first element of values is null.

Join(String, Object[]) 是一种简便方法,可让你连接对象数组中的每个元素,而无需将其元素显式转换为字符串。Join(String, Object[]) is a convenience method that lets you concatenate each element in an object array without explicitly converting its elements to strings. 数组中每个对象的字符串表示形式都是通过调用该对象的 ToString 方法派生的。The string representation of each object in the array is derived by calling that object's ToString method.

调用方说明

如果 nullvalues 的第一个元素,则 Join(String, Object[]) 方法不会连接 values 中的元素,而是返回 EmptyIf the first element of values is null, the Join(String, Object[]) method does not concatenate the elements in values but instead returns Empty. 此问题有多种解决方法。A number of workarounds for this issue are available. 最简单的方法是将 Empty 的值分配给数组的第一个元素,如下面的示例所示。The easiest is to assign a value of Empty to the first element of the array, as the following example shows.

[!code-csharpSystem.String.Join#6] [!code-vbSystem.String.Join#6][!code-csharpSystem.String.Join#6] [!code-vbSystem.String.Join#6]

另请参阅

Join(String, String[])

串联字符串数组的所有元素,其中在每个元素之间使用指定的分隔符。Concatenates all the elements of a string array, using the specified separator between each element.

public:
 static System::String ^ Join(System::String ^ separator, cli::array <System::String ^> ^ value);
public static string Join (string separator, string[] value);
static member Join : string * string[] -> string
Public Shared Function Join (separator As String, value As String()) As String

参数

separator
String

要用作分隔符的字符串。The string to use as a separator. 只有在 separator 具有多个元素时,value 才包括在返回的字符串中。separator is included in the returned string only if value has more than one element.

value
String[]

一个数组,其中包含要连接的元素。An array that contains the elements to concatenate.

返回

一个由 value 中的元素组成的字符串,这些元素以 separator 字符串分隔。A string that consists of the elements in value delimited by the separator string. 如果 value 为空数组,该方法将返回 EmptyIf value is an empty array, the method returns Empty.

异常

valuenullvalue is null.

生成的字符串长度超出了允许的最大长度 (MaxValue)。The length of the resulting string overflows the maximum allowed length (MaxValue).

示例

下面的示例演示 Join 方法。The following example demonstrates the Join method.

using namespace System;
String^ MakeLine( int initVal, int multVal, String^ sep )
{
   array<String^>^sArr = gcnew array<String^>(10);
   for ( int i = initVal; i < initVal + 10; i++ )
      sArr[ i - initVal ] = String::Format( "{0, -3}", i * multVal );
   return String::Join( sep, sArr );
}

int main()
{
   Console::WriteLine( MakeLine( 0, 5, ", " ) );
   Console::WriteLine( MakeLine( 1, 6, "  " ) );
   Console::WriteLine( MakeLine( 9, 9, ": " ) );
   Console::WriteLine( MakeLine( 4, 7, "< " ) );
}
// The example displays the following output:
//       0  , 5  , 10 , 15 , 20 , 25 , 30 , 35 , 40 , 45
//       6    12   18   24   30   36   42   48   54   60
//       81 : 90 : 99 : 108: 117: 126: 135: 144: 153: 162
//       28 < 35 < 42 < 49 < 56 < 63 < 70 < 77 < 84 < 91
using System;

public class JoinTest 
{
    public static void Main() 
    {
        Console.WriteLine(MakeLine(0, 5, ", "));
        Console.WriteLine(MakeLine(1, 6, "  "));
        Console.WriteLine(MakeLine(9, 9, ": "));
        Console.WriteLine(MakeLine(4, 7, "< "));
    }

    private static string MakeLine(int initVal, int multVal, string sep) 
    {
        string [] sArr = new string [10];

        for (int i = initVal; i < initVal + 10; i++)
            sArr[i - initVal] = String.Format("{0,-3}", i * multVal);

        return String.Join(sep, sArr);
    }
}
// The example displays the following output:
//       0  , 5  , 10 , 15 , 20 , 25 , 30 , 35 , 40 , 45
//       6    12   18   24   30   36   42   48   54   60
//       81 : 90 : 99 : 108: 117: 126: 135: 144: 153: 162
//       28 < 35 < 42 < 49 < 56 < 63 < 70 < 77 < 84 < 91  
Public Class JoinTest
    
    Public Shared Sub Main()
        
        Console.WriteLine(MakeLine(0, 5, ", "))
        Console.WriteLine(MakeLine(1, 6, "  "))
        Console.WriteLine(MakeLine(9, 9, ": "))
        Console.WriteLine(MakeLine(4, 7, "< "))
    End Sub
    
    
    Private Shared Function MakeLine(initVal As Integer, multVal As Integer, sep As String) As String
        Dim sArr(10) As String
        Dim i As Integer
        
        
        For i = initVal To (initVal + 10) - 1
            sArr((i - initVal)) = [String].Format("{0,-3}", i * multVal)
        
        Next i
        Return [String].Join(sep, sArr)
    End Function 'MakeLine
End Class
' The example displays the following output:
'       0  , 5  , 10 , 15 , 20 , 25 , 30 , 35 , 40 , 45
'       6    12   18   24   30   36   42   48   54   60
'       81 : 90 : 99 : 108: 117: 126: 135: 144: 153: 162
'       28 < 35 < 42 < 49 < 56 < 63 < 70 < 77 < 84 < 91

注解

例如,如果 separator 为 "," 并且 value 的元素为 "apple"、"橙色"、"grape" 和 "梨",Join(separator, value) 将返回 "apple,橙色,grape,梨"。For example, if separator is ", " and the elements of value are "apple", "orange", "grape", and "pear", Join(separator, value) returns "apple, orange, grape, pear".

如果 null``separator,则改为使用空字符串(String.Empty)。If separator is null, an empty string (String.Empty) is used instead. 如果 null``value 中的任何元素,则改为使用空字符串。If any element in value is null, an empty string is used instead.

另请参阅

Join(Char, String[], Int32, Int32)

连接字符串数组,其中在每个成员之间使用指定的分隔符,并且从位于 startIndex 位置的 value 中的元素开始,并连接多达 count 个元素。Concatenates an array of strings, using the specified separator between each member, starting with the element in value located at the startIndex position, and concatenating up to count elements.

public:
 static System::String ^ Join(char separator, cli::array <System::String ^> ^ value, int startIndex, int count);
public static string Join (char separator, string[] value, int startIndex, int count);
static member Join : char * string[] * int * int -> string
Public Shared Function Join (separator As Char, value As String(), startIndex As Integer, count As Integer) As String

参数

separator
Char

连接字符串数组,其中在每个成员之间使用指定的分隔符,并且从位于指定索引处的元素开始,并包含指定数量的元素。Concatenates an array of strings, using the specified separator between each member, starting with the element located at the specified index and including a specified number of elements.

value
String[]

要连接的字符串数组。An array of strings to concatenate.

startIndex
Int32

要连接的 value 中的第一个项。The first item in value to concatenate.

count
Int32

要连接的 value 中的元素数,从位于 startIndex 位置的元素开始。The number of elements from value to concatenate, starting with the element in the startIndex position.

返回

一个由 value 的元素组成的字符串,这些元素以 separator 字符分隔。A string that consists of the elements of value delimited by the separator character.

-or-

如果 count 为零,value 没有元素,或 value 的全部元素均为 nullEmpty,则为 EmptyEmpty if count is zero, value has no elements, or all the elements of value are null or Empty.

异常

valuenullvalue is null.

startIndexcount 为负。startIndex or count are negative.

-or-

startIndex 大于 value 的长度 - countstartIndex is greater than the length of value - count.

生成的字符串长度超出了允许的最大长度 (MaxValue)。The length of the resulting string overflows the maximum allowed length (MaxValue).

Join(String, String[], Int32, Int32)

串联字符串数组的指定元素,其中在每个元素之间使用指定的分隔符。Concatenates the specified elements of a string array, using the specified separator between each element.

public:
 static System::String ^ Join(System::String ^ separator, cli::array <System::String ^> ^ value, int startIndex, int count);
public static string Join (string separator, string[] value, int startIndex, int count);
static member Join : string * string[] * int * int -> string
Public Shared Function Join (separator As String, value As String(), startIndex As Integer, count As Integer) As String

参数

separator
String

要用作分隔符的字符串。The string to use as a separator. 只有在 separator 具有多个元素时,value 才包括在返回的字符串中。separator is included in the returned string only if value has more than one element.

value
String[]

一个数组,其中包含要连接的元素。An array that contains the elements to concatenate.

startIndex
Int32

value 中要使用的第一个元素。The first element in value to use.

count
Int32

要使用的 value 的元素数。The number of elements of value to use.

返回

value 中的字符串组成的字符串,这些字符串以 separator 字符串分隔。A string that consists of the strings in value delimited by the separator string.

-or- 如果 Empty 为零,count 没有元素,或 value 以及 separator 的全部元素均为 value,则为 EmptyEmpty if count is zero, value has no elements, or separator and all the elements of value are Empty.

异常

valuenullvalue is null.

startIndexcount 小于 0。startIndex or count is less than 0.

-or-

startIndex 加上 count 大于 value中的元素数。startIndex plus count is greater than the number of elements in value.

内存不足。Out of memory.

示例

下面的示例连接水果名称数组中的两个元素。The following example concatenates two elements from an array of names of fruit.

// Sample for String::Join(String, String[], int int)
using namespace System;
int main()
{
   array<String^>^val = {"apple","orange","grape","pear"};
   String^ sep = ", ";
   String^ result;
   Console::WriteLine( "sep = '{0}'", sep );
   Console::WriteLine( "val[] = {{'{0}' '{1}' '{2}' '{3}'}}", val[ 0 ], val[ 1 ], val[ 2 ], val[ 3 ] );
   result = String::Join( sep, val, 1, 2 );
   Console::WriteLine( "String::Join(sep, val, 1, 2) = '{0}'", result );
}

/*
This example produces the following results:
sep = ', '
val[] = {'apple' 'orange' 'grape' 'pear'}
String::Join(sep, val, 1, 2) = 'orange, grape'
*/
String[] val = {"apple", "orange", "grape", "pear"};
String sep   = ", ";
String result;

Console.WriteLine("sep = '{0}'", sep);
Console.WriteLine("val[] = {{'{0}' '{1}' '{2}' '{3}'}}", val[0], val[1], val[2], val[3]);
result = String.Join(sep, val, 1, 2);
Console.WriteLine("String.Join(sep, val, 1, 2) = '{0}'", result);

// This example produces the following results:
// sep = ', '
// val[] = {'apple' 'orange' 'grape' 'pear'}
// String.Join(sep, val, 1, 2) = 'orange, grape'
Class Sample
   Public Shared Sub Main()
      Dim val As [String]() =  {"apple", "orange", "grape", "pear"}
      Dim sep As [String] = ", "
      Dim result As [String]
      
      Console.WriteLine("sep = '{0}'", sep)
      Console.WriteLine("val() = {{'{0}' '{1}' '{2}' '{3}'}}", val(0), val(1), val(2), val(3))
      result = [String].Join(sep, val, 1, 2)
      Console.WriteLine("String.Join(sep, val, 1, 2) = '{0}'", result)
   End Sub
End Class 
'This example displays the following output:
'       sep = ', '
'       val() = {'apple' 'orange' 'grape' 'pear'}
'       String.Join(sep, val, 1, 2) = 'orange, grape'

注解

例如,如果 separator 为 "," 且 value 的元素为 "apple"、"橙色"、"grape" 和 "梨",Join(separator, value, 1, 2) 将返回 "橙色,grape"。For example, if separator is ", " and the elements of value are "apple", "orange", "grape", and "pear", Join(separator, value, 1, 2) returns "orange, grape".

如果 null``separator,则改为使用空字符串(String.Empty)。If separator is null, an empty string (String.Empty) is used instead. 如果 null``value 中的任何元素,则改为使用空字符串。If any element in value is null, an empty string is used instead.

另请参阅

Join<T>(Char, IEnumerable<T>)

串联集合的成员,其中在每个成员之间使用指定的分隔符。Concatenates the members of a collection, using the specified separator between each member.

public:
generic <typename T>
 static System::String ^ Join(char separator, System::Collections::Generic::IEnumerable<T> ^ values);
public static string Join<T> (char separator, System.Collections.Generic.IEnumerable<T> values);
static member Join : char * seq<'T> -> string
Public Shared Function Join(Of T) (separator As Char, values As IEnumerable(Of T)) As String

类型参数

T

values 成员的类型。The type of the members of values.

参数

separator
Char

要用作分隔符的字符。The character to use as a separator. 只有在 separator 具有多个元素时,values 才包括在返回的字符串中。separator is included in the returned string only if values has more than one element.

values
IEnumerable<T>

一个包含要串联的对象的集合。A collection that contains the objects to concatenate.

返回

一个由 values 的成员组成的字符串,这些成员以 separator 字符分隔。A string that consists of the members of values delimited by the separator character. 如果 values 没有成员,则该方法返回 EmptyIf values has no members, the method returns Empty.

异常

valuesnullvalues is null.

生成的字符串长度超出了允许的最大长度 (MaxValue)。The length of the resulting string overflows the maximum allowed length (MaxValue).

Join<T>(String, IEnumerable<T>)

串联集合的成员,其中在每个成员之间使用指定的分隔符。Concatenates the members of a collection, using the specified separator between each member.

public:
generic <typename T>
 static System::String ^ Join(System::String ^ separator, System::Collections::Generic::IEnumerable<T> ^ values);
[System.Runtime.InteropServices.ComVisible(false)]
public static string Join<T> (string separator, System.Collections.Generic.IEnumerable<T> values);
static member Join : string * seq<'T> -> string
Public Shared Function Join(Of T) (separator As String, values As IEnumerable(Of T)) As String

类型参数

T

values 成员的类型。The type of the members of values.

参数

separator
String

要用作分隔符的字符串。The string to use as a separator. 只有在 separator 具有多个元素时,values 才包括在返回的字符串中。separator is included in the returned string only if values has more than one element.

values
IEnumerable<T>

一个包含要串联的对象的集合。A collection that contains the objects to concatenate.

返回

一个由 values 的成员组成的字符串,这些成员以 separator 字符串分隔。A string that consists of the members of values delimited by the separator string. 如果 values 没有成员,则该方法返回 EmptyIf values has no members, the method returns Empty.

属性

异常

valuesnullvalues is null.

生成的字符串长度超出了允许的最大长度 (MaxValue)。The length of the resulting string overflows the maximum allowed length (MaxValue).

示例

下面的示例使用埃拉托色 of 尼斯筛法算法来计算小于或等于100的质数。The following example uses the Sieve of Eratosthenes algorithm to calculate the prime numbers that are less than or equal to 100. 它将结果分配给类型为 integer 的 List<T> 对象,然后将其传递给 Join<T>(String, IEnumerable<T>) 方法。It assigns the result to a List<T> object of type integer, which it then passes to the Join<T>(String, IEnumerable<T>) method.

using System;
using System.Collections.Generic;

public class Example
{
   public static void Main()
   {
      int maxPrime = 100;
      List<int> primes = GetPrimes(maxPrime);
      Console.WriteLine("Primes less than {0}:", maxPrime);
      Console.WriteLine("   {0}", String.Join(" ", primes));
   }

   private static List<int> GetPrimes(int maxPrime)
   {
      Array values = Array.CreateInstance(typeof(int), 
                              new int[] { maxPrime - 1}, new int[] { 2 });
      // Use Sieve of Eratosthenes to determine prime numbers.
      for (int ctr = values.GetLowerBound(0); ctr <= (int) Math.Ceiling(Math.Sqrt(values.GetUpperBound(0))); ctr++)
      {
                           
         if ((int) values.GetValue(ctr) == 1) continue;
         
         for (int multiplier = ctr; multiplier <=  maxPrime / 2; multiplier++)
            if (ctr * multiplier <= maxPrime)
               values.SetValue(1, ctr * multiplier);
      }      
      
      List<int> primes = new List<int>();
      for (int ctr = values.GetLowerBound(0); ctr <= values.GetUpperBound(0); ctr++)
         if ((int) values.GetValue(ctr) == 0) 
            primes.Add(ctr);
      return primes;
   }   
}
// The example displays the following output:
//    Primes less than 100:
//       2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97
Imports System.Collections.Generic

Module Example
   Public Sub Main()
      Dim maxPrime As Integer = 100
      Dim primes As List(Of Integer) = GetPrimes(maxPrime)
      Console.WriteLine("Primes less than {0}:", maxPrime)
      Console.WriteLine("   {0}", String.Join(" ", primes))
   End Sub
   
   Private Function GetPrimes(maxPrime As Integer) As List(Of Integer)
      Dim values As Array = Array.CreateInstance(GetType(Integer), _
                              New Integer() { maxPrime - 1}, New Integer(){ 2 }) 
        ' Use Sieve of Eratosthenes to determine prime numbers.
      For ctr As Integer = values.GetLowerBound(0) To _
                           CInt(Math.Ceiling(Math.Sqrt(values.GetUpperBound(0))))
         If CInt(values.GetValue(ctr)) = 1 Then Continue For
         
         For multiplier As Integer = ctr To maxPrime \ 2
            If ctr * multiplier <= maxPrime Then values.SetValue(1, ctr * multiplier)
         Next   
      Next      
      
      Dim primes As New System.Collections.Generic.List(Of Integer)
      For ctr As Integer = values.GetLowerBound(0) To values.GetUpperBound(0)
         If CInt(values.GetValue(ctr)) = 0 Then primes.Add(ctr)
      Next            
      Return primes
   End Function   
End Module
' The example displays the following output:
'    Primes less than 100:
'       2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97

注解

如果 null``separator,则改为使用空字符串(String.Empty)。If separator is null, an empty string (String.Empty) is used instead. 如果 null``values 的任何成员,则改为使用空字符串。If any member of values is null, an empty string is used instead.

Join<T>(String, IEnumerable<T>) 是一种简便方法,使你可以连接 IEnumerable<T> 集合的每个成员,无需先将其转换为字符串。Join<T>(String, IEnumerable<T>) is a convenience method that lets you concatenate each member of an IEnumerable<T> collection without first converting them to strings. IEnumerable<T> 集合中每个对象的字符串表示形式是通过调用该对象的 ToString 方法派生的。The string representation of each object in the IEnumerable<T> collection is derived by calling that object's ToString method.

此方法对语言集成查询(LINQ)查询表达式特别有用。This method is particular useful with Language-Integrated Query (LINQ) query expressions. 例如,下面的代码定义了一个非常简单的 Animal 类,该类包含动物的名称以及其所属的顺序。For example, the following code defines a very simple Animal class that contains the name of an animal and the order to which it belongs. 然后,它定义包含多个 Animal 对象的 List<T> 对象。It then defines a List<T> object that contains a number of Animal objects. 调用 Enumerable.Where 扩展方法以提取其 Order 属性等于 "啮齿类" 的 Animal 对象。The Enumerable.Where extension method is called to extract the Animal objects whose Order property equals "Rodent". 结果传递给 Join<T>(String, IEnumerable<T>) 方法。The result is passed to the Join<T>(String, IEnumerable<T>) method.

using System;
using System.Collections.Generic;
using System.Linq;

public class Animal
{
   public string Kind;
   public string Order;
   
   public Animal(string kind, string order)
   {
      this.Kind = kind;
      this.Order = order;
   }
   
   public override string ToString()
   {
      return this.Kind;
   }
}

public class Example
{
   public static void Main()
   {
      List<Animal> animals = new List<Animal>();
      animals.Add(new Animal("Squirrel", "Rodent"));
      animals.Add(new Animal("Gray Wolf", "Carnivora"));
      animals.Add(new Animal("Capybara", "Rodent"));
      string output = String.Join(" ", animals.Where( animal => 
                      (animal.Order == "Rodent")));
      Console.WriteLine(output);  
   }
}
// The example displays the following output:
//      Squirrel Capybara
Imports System.Collections.Generic

Public Class Animal
   Public Kind As String
   Public Order As String
   
   Public Sub New(kind As String, order As String)
      Me.Kind = kind
      Me.Order = order
   End Sub
   
   Public Overrides Function ToString() As String
      Return Me.Kind
   End Function
End Class

Module Example
   Public Sub Main()
      Dim animals As New List(Of Animal)
      animals.Add(New Animal("Squirrel", "Rodent"))
      animals.Add(New Animal("Gray Wolf", "Carnivora"))
      animals.Add(New Animal("Capybara", "Rodent")) 
      Dim output As String = String.Join(" ", animals.Where(Function(animal) _
                                           animal.Order = "Rodent"))
      Console.WriteLine(output)                                           
   End Sub
End Module
' The example displays the following output:
'      Squirrel Capybara

另请参阅

适用于