TextReader 类

定义

public ref class TextReader abstract : IDisposable

public ref class TextReader abstract : MarshalByRefObject, IDisposable

public abstract class TextReader : IDisposable

[System.Serializable]
public abstract class TextReader : MarshalByRefObject, IDisposable

[System.Serializable]
[System.Runtime.InteropServices.ComVisible(true)]
public abstract class TextReader : MarshalByRefObject, IDisposable

public abstract class TextReader : MarshalByRefObject, IDisposable

type TextReader = class
    interface IDisposable

[<System.Serializable>]
type TextReader = class
    inherit MarshalByRefObject
    interface IDisposable

[<System.Serializable>]
[<System.Runtime.InteropServices.ComVisible(true)>]
type TextReader = class
    inherit MarshalByRefObject
    interface IDisposable

type TextReader = class
    inherit MarshalByRefObject
    interface IDisposable

Public MustInherit Class TextReader
Implements IDisposable

Public MustInherit Class TextReader
Inherits MarshalByRefObject
Implements IDisposable

继承

Object

TextReader

继承

Object

MarshalByRefObject

TextReader

派生

System.IO.StreamReader

System.IO.StringReader

属性

SerializableAttribute ComVisibleAttribute

实现

IDisposable

示例

该 TextReader 类是一个抽象类。 因此，不会在代码中实例化它。 该 StreamReader 类派生自 TextReader 成员的实现，以便从流中读取。 以下示例演示如何使用 StreamReader.ReadAsync(Char[], Int32, Int32) 该方法读取文件中的所有字符。 在将字符添加到类的 StringBuilder 实例之前，它会检查每个字符是字母、数字还是空格。

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

namespace WpfApplication
{
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private async void Button_Click_1(object sender, RoutedEventArgs e)
        {
            string filename = @"C:\Example\existingfile.txt";
            char[] result;
            StringBuilder builder = new StringBuilder();

            using (StreamReader reader = File.OpenText(filename))
            {
                result = new char[reader.BaseStream.Length];
                await reader.ReadAsync(result, 0, (int)reader.BaseStream.Length);
            }

            foreach (char c in result)
            {
                if (char.IsLetterOrDigit(c) || char.IsWhiteSpace(c))
                {
                    builder.Append(c);
                }
            }
            FileOutput.Text = builder.ToString();
        }
    }
}

Imports System.Text
Imports System.IO

Class MainWindow

    Private Async Sub Button_Click_1(sender As Object, e As RoutedEventArgs)
        Dim filename As String = "C:\Example\existingfile.txt"
        Dim result() As Char
        Dim builder As StringBuilder = New StringBuilder()

        Using reader As StreamReader = File.OpenText(filename)
            ReDim result(reader.BaseStream.Length)
            Await reader.ReadAsync(result, 0, reader.BaseStream.Length)
        End Using

        For Each c As Char In result
            If (Char.IsLetterOrDigit(c) Or Char.IsWhiteSpace(c)) Then
                builder.Append(c)
            End If
            Next
        FileOutput.Text = builder.ToString()
    End Sub
End Class

注解

TextReader是抽象基类StreamReaderStringReader，分别从流和字符串读取字符。 使用这些派生类打开文本文件以读取指定的字符范围，或基于现有流创建读取器。

实施者说明

派生类必须至少实现 Peek() 这些类和 Read() 方法才能生成有用的实例 TextReader。

另请参阅

• StringReader
• StreamReader
• 文件和流输入/输出
• 如何：从文件读取文本
• 如何：将文本写入文件
• 如何：读取和写入新创建的数据文件