Procedura: leggere caratteri da una stringaHow to: Read characters from a string

Gli esempi di codice seguenti illustrano come leggere i caratteri in modo sincrono o asincrono da una stringa.The following code examples show how to read characters synchronously or asynchronously from a string.

Esempio: leggere i caratteri in modo sincronoExample: Read characters synchronously

Questo esempio legge 13 caratteri in modo sincrono da una stringa, li archivia in una matrice e li visualizza.This example reads 13 characters synchronously from a string, stores them in an array, and displays them. Legge quindi i caratteri rimanenti nella stringa, li archivia nella matrice a partire dal sesto elemento e visualizza il contenuto della matrice.The example then reads the rest of the characters in the string, stores them in the array starting at the sixth element, and displays the contents of the array.

using System;
using System.IO;

public class CharsFromStr
{
    public static void Main()
    {
        string str = "Some number of characters";
        char[] b = new char[str.Length];

        using (StringReader sr = new StringReader(str))
        {
            // Read 13 characters from the string into the array.
            sr.Read(b, 0, 13);
            Console.WriteLine(b);

            // Read the rest of the string starting at the current string position.
            // Put in the array starting at the 6th array member.
            sr.Read(b, 5, str.Length - 13);
            Console.WriteLine(b);
        }
    }
}
// The example has the following output:
//
// Some number o
// Some f characters
Imports System.IO

Public Class CharsFromStr
    Public Shared Sub Main()
        Dim str As String = "Some number of characters"
        Dim b(str.Length - 1) As Char

        Using sr As StringReader = New StringReader(str)
            ' Read 13 characters from the string into the array.
            sr.Read(b, 0, 13)
            Console.WriteLine(b)

            ' Read the rest of the string starting at the current string position.
            ' Put in the array starting at the 6th array member.
            sr.Read(b, 5, str.Length - 13)
            Console.WriteLine(b)
        End Using
    End Sub
End Class
' The example has the following output:
'
' Some number o
' Some f characters

Esempio: leggere i caratteri in modo asincronoExample: Read characters asynchronously

L'esempio successivo è il code-behind di un'app WPF.The next example is the code behind a WPF app. Al caricamento della finestra, l'esempio legge in modo asincrono tutti i caratteri da un controllo TextBox e li archivia in una matrice.On window load, the example asynchronously reads all characters from a TextBox control and stores them in an array. Scrive quindi in modo asincrono ogni lettera o spazio su una riga separata di un controllo TextBlock.It then asynchronously writes each letter or white-space character to a separate line of a TextBlock control.

using System;
using System.Text;
using System.Windows;
using System.IO;

namespace StringReaderWriter
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private async void Window_Loaded(object sender, RoutedEventArgs e)
        {
            char[] charsRead = new char[UserInput.Text.Length];
            using (StringReader reader = new StringReader(UserInput.Text))
            {
                await reader.ReadAsync(charsRead, 0, UserInput.Text.Length);
            }

            StringBuilder reformattedText = new StringBuilder();
            using (StringWriter writer = new StringWriter(reformattedText))
            {
                foreach (char c in charsRead)
                {
                    if (char.IsLetter(c) || char.IsWhiteSpace(c))
                    {
                        await writer.WriteLineAsync(char.ToLower(c));
                    }
                }
            }
            Result.Text = reformattedText.ToString();
        }
    }
}
Imports System.IO
Imports System.Text

''' <summary>
''' Interaction logic for MainWindow.xaml
''' </summary>

Partial Public Class MainWindow
    Inherits Window
    Public Sub New()
        InitializeComponent()
    End Sub
    Private Async Sub Window_Loaded(sender As Object, e As RoutedEventArgs)
        Dim charsRead As Char() = New Char(UserInput.Text.Length) {}
        Using reader As StringReader = New StringReader(UserInput.Text)
            Await reader.ReadAsync(charsRead, 0, UserInput.Text.Length)
        End Using

        Dim reformattedText As StringBuilder = New StringBuilder()
        Using writer As StringWriter = New StringWriter(reformattedText)
            For Each c As Char In charsRead
                If Char.IsLetter(c) Or Char.IsWhiteSpace(c) Then
                    Await writer.WriteLineAsync(Char.ToLower(c))
                End If
            Next
        End Using
        Result.Text = reformattedText.ToString()
    End Sub
End Class

Vedere ancheSee also