String.Join Method
Definition
Concatenates the elements of a specified array or the members of a collection, using the specified separator between each element or member.
Overloads
Join(Char, Object[]) |
Concatenates the string representations of an array of objects, using the specified separator between each member. |
Join(Char, String[]) |
Concatenates an array of strings, using the specified separator between each member. |
Join(String, IEnumerable<String>) |
Concatenates the members of a constructed IEnumerable<T> collection of type String, using the specified separator between each member. |
Join(String, Object[]) |
Concatenates the elements of an object array, using the specified separator between each element. |
Join(String, String[]) |
Concatenates all the elements of a string array, using the specified separator between each element. |
Join(Char, String[], Int32, Int32) |
Concatenates an array of strings, using the specified separator between each member, starting with the element in |
Join(String, String[], Int32, Int32) |
Concatenates the specified elements of a string array, using the specified separator between each element. |
Join<T>(Char, IEnumerable<T>) |
Concatenates the members of a collection, using the specified separator between each member. |
Join<T>(String, IEnumerable<T>) |
Concatenates the members of a collection, using the specified separator between each member. |
Join(Char, Object[])
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);
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
Parameters
- separator
- Char
The character to use as a separator. separator
is included in the returned string only if value
has more than one element.
- values
- Object[]
An array of objects whose string representations will be concatenated.
Returns
A string that consists of the elements of values
delimited by the separator
character.
-or-
Empty if values
has zero elements or all the elements of values
are null
.
Exceptions
value
is null
.
The length of the resulting string overflows the maximum allowed length (MaxValue).
Applies to
Join(Char, String[])
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);
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
Parameters
- separator
- Char
The character to use as a separator. separator
is included in the returned string only if value
has more than one element.
- value
- String[]
An array of strings to concatenate.
Returns
A string that consists of the elements of value
delimited by the separator
character.
-or-
Empty if value
has zero elements or all the elements of value
are null
.
Exceptions
value
is null
.
The length of the resulting string overflows the maximum allowed length (MaxValue).
Applies to
Join(String, IEnumerable<String>)
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);
public static string Join (string separator, System.Collections.Generic.IEnumerable<string> values);
public static string Join (string? separator, System.Collections.Generic.IEnumerable<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
[<System.Runtime.InteropServices.ComVisible(false)>]
static member Join : string * seq<string> -> string
Public Shared Function Join (separator As String, values As IEnumerable(Of String)) As String
Parameters
- separator
- String
The string to use as a separator.separator
is included in the returned string only if values
has more than one element.
- values
- IEnumerable<String>
A collection that contains the strings to concatenate.
Returns
A string that consists of the members of values
delimited by the separator
string.
-or-
Empty if values
has zero elements or all the elements of values
are null
.
- Attributes
Exceptions
values
is null
.
The length of the resulting string overflows the maximum allowed length (MaxValue).
Examples
The following example uses the Sieve of Eratosthenes algorithm to calculate the prime numbers that are less than or equal to 100. 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
Remarks
If separator
is null
, an empty string (String.Empty) is used instead. If any member of values
is null
, an empty string is used instead.
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. It is particularly useful with Language-Integrated Query (LINQ) query expressions. 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"). 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
See also
Applies to
Join(String, Object[])
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);
public static string Join (string separator, params object[] values);
public static string Join (string? separator, params object[]? values);
[System.Runtime.InteropServices.ComVisible(false)]
public static string Join (string separator, params object[] values);
static member Join : string * obj[] -> string
[<System.Runtime.InteropServices.ComVisible(false)>]
static member Join : string * obj[] -> string
Public Shared Function Join (separator As String, ParamArray values As Object()) As String
Parameters
- separator
- String
The string to use as a separator. separator
is included in the returned string only if values
has more than one element.
- values
- Object[]
An array that contains the elements to concatenate.
Returns
A string that consists of the elements of values
delimited by the separator
string. If values
is an empty array, the method returns Empty.
- Attributes
Exceptions
values
is null
.
The length of the resulting string overflows the maximum allowed length (MaxValue).
Examples
The following example uses the Sieve of Eratosthenes algorithm to calculate the prime numbers that are less than or equal to 100. 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
Remarks
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. See the Notes for Callers section if the first element of values
is null
.
Join(String, Object[]) is a convenience method that lets you concatenate each element in an object array without explicitly converting its elements to strings. The string representation of each object in the array is derived by calling that object's ToString
method.
Notes to Callers
If the first element of values
is null
, the Join(String, Object[]) method does not concatenate the elements in values
but instead returns Empty. A number of workarounds for this issue are available. The easiest is to assign a value of Empty to the first element of the array, as the following example shows.
object[] values = { null, "Cobb", 4189, 11434, .366 };
if (values[0] == null) values[0] = String.Empty;
Console.WriteLine(String.Join("|", values));
// The example displays the following output:
// |Cobb|4189|11434|0.366
Dim values() As Object = { Nothing, "Cobb", 4189, 11434, .366 }
If values(0) Is Nothing Then values(0) = String.Empty
Console.WriteLine(String.Join("|", values))
' The example displays the following output:
' |Cobb|4189|11434|0.366
See also
Applies to
Join(String, String[])
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 System::String ^ Join(System::String ^ separator, cli::array <System::String ^> ^ value);
public static string Join (string separator, params string[] value);
public static string Join (string? separator, params string[]? value);
public static string Join (string separator, string[] value);
static member Join : string * string[] -> string
Public Shared Function Join (separator As String, ParamArray value As String()) As String
Public Shared Function Join (separator As String, value As String()) As String
Parameters
- separator
- String
The string to use as a separator. separator
is included in the returned string only if value
has more than one element.
- value
- String[]
An array that contains the elements to concatenate.
Returns
A string that consists of the elements in value
delimited by the separator
string. If value
is an empty array, the method returns Empty.
Exceptions
value
is null
.
The length of the resulting string overflows the maximum allowed length (MaxValue).
Examples
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
Remarks
For example, if separator
is ", " and the elements of value
are "apple", "orange", "grape", and "pear", Join(separator, value)
returns "apple, orange, grape, pear".
If separator
is null
, an empty string (String.Empty) is used instead. If any element in value
is null
, an empty string is used instead.
See also
Applies to
Join(Char, String[], Int32, Int32)
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);
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
Parameters
- separator
- Char
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[]
An array of strings to concatenate.
- startIndex
- Int32
The first item in value
to concatenate.
- count
- Int32
The number of elements from value
to concatenate, starting with the element in the startIndex
position.
Returns
A string that consists of the elements of value
delimited by the separator
character.
-or-
Empty if count
is zero, value
has no elements, or all the elements of value
are null
or Empty.
Exceptions
value
is null
.
startIndex
or count
are negative.
-or-
startIndex
is greater than the length of value
- count
.
The length of the resulting string overflows the maximum allowed length (MaxValue).
Applies to
Join(String, String[], Int32, Int32)
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);
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
Parameters
- separator
- String
The string to use as a separator. separator
is included in the returned string only if value
has more than one element.
- value
- String[]
An array that contains the elements to concatenate.
- startIndex
- Int32
The first element in value
to use.
- count
- Int32
The number of elements of value
to use.
Returns
A string that consists of the strings in value
delimited by the separator
string.
-or-
Empty if count
is zero, value
has no elements, or separator
and all the elements of value
are Empty.
Exceptions
value
is null
.
startIndex
or count
is less than 0.
-or-
startIndex
plus count
is greater than the number of elements in value
.
Out of memory.
Examples
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'
Remarks
For example, if separator
is ", " and the elements of value
are "apple", "orange", "grape", and "pear", Join(separator, value, 1, 2)
returns "orange, grape".
If separator
is null
, an empty string (String.Empty) is used instead. If any element in value
is null
, an empty string is used instead.
See also
Applies to
Join<T>(Char, IEnumerable<T>)
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
Type Parameters
- T
The type of the members of values
.
Parameters
- separator
- Char
The character to use as a separator. separator
is included in the returned string only if values
has more than one element.
- values
- IEnumerable<T>
A collection that contains the objects to concatenate.
Returns
A string that consists of the members of values
delimited by the separator
character. If values
has no members, the method returns Empty.
Exceptions
values
is null
.
The length of the resulting string overflows the maximum allowed length (MaxValue).
Applies to
Join<T>(String, IEnumerable<T>)
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);
public static string Join<T> (string separator, System.Collections.Generic.IEnumerable<T> values);
public static string Join<T> (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
[<System.Runtime.InteropServices.ComVisible(false)>]
static member Join : string * seq<'T> -> string
Public Shared Function Join(Of T) (separator As String, values As IEnumerable(Of T)) As String
Type Parameters
- T
The type of the members of values
.
Parameters
- separator
- String
The string to use as a separator. separator
is included in the returned string only if values
has more than one element.
- values
- IEnumerable<T>
A collection that contains the objects to concatenate.
Returns
A string that consists of the members of values
delimited by the separator
string. If values
has no members, the method returns Empty.
- Attributes
Exceptions
values
is null
.
The length of the resulting string overflows the maximum allowed length (MaxValue).
Examples
The following example uses the Sieve of Eratosthenes algorithm to calculate the prime numbers that are less than or equal to 100. 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
Remarks
If separator
is null
, an empty string (String.Empty) is used instead. If any member of values
is null
, an empty string is used instead.
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. The string representation of each object in the IEnumerable<T> collection is derived by calling that object's ToString
method.
This method is particular useful with Language-Integrated Query (LINQ) query expressions. 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. It then defines a List<T> object that contains a number of Animal
objects. The Enumerable.Where extension method is called to extract the Animal
objects whose Order
property equals "Rodent". 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