如何：从字符串中读取字符
下面的代码示例展示了如何从字符串中异步或同步读取字符。
示例：同步读取字符
此示例从字符串中同步读取 13 个字符，将它们存储到数组中，并显示这些字符。 然后，示例将读取字符串中的剩余字符，将它们存储到数组中（从第六个元素开始），并显示数组的内容。
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
示例：异步读取字符
下一个示例是 WPF 应用背后的代码。 在窗口加载时，示例从 TextBox 控件异步读取所有字符，并将其存储在数组中。 随后，它以异步方式将每个字母或空格字符写入单独的 TextBlock 控件行。
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
