XmlWriter.WriteProcessingInstruction(String, String) 方法

定义

命名空间:

System.Xml

程序集:

System.Xml.ReaderWriter.dll

Source:

XmlWriter.cs

当在派生类中被重写时，写出在名称和文本之间带有空格的处理指令，如下所示：<?name text?>。

public:
 abstract void WriteProcessingInstruction(System::String ^ name, System::String ^ text);

public abstract void WriteProcessingInstruction (string name, string? text);

abstract member WriteProcessingInstruction : string * string -> unit

Public MustOverride Sub WriteProcessingInstruction (name As String, text As String)

参数

name

String

处理指令的名称。

text

String

要包括在处理指令中的文本。

例外

ArgumentException

该文本将导致格式不正确的 XML 文档。

name 为 null 或 String.Empty。

调用了 WriteStartDocument() 后，使用此方法创建 XML 声明。

InvalidOperationException

在上一次异步操作完成之前调用了 XmlWriter 方法。 在此情况下，会引发 InvalidOperationException 并显示消息“异步操作已在进行中。”

示例

以下示例编写一个表示书籍的 XML 文件。

using System;
using System.IO;
using System.Xml;

public class Sample {

  private const string filename = "sampledata.xml";

  public static void Main() {

     XmlWriterSettings settings = new XmlWriterSettings();
     settings.Indent = true;
     XmlWriter writer = XmlWriter.Create(filename, settings);

     // Write the Processing Instruction node.
     String PItext="type=\"text/xsl\" href=\"book.xsl\"";
     writer.WriteProcessingInstruction("xml-stylesheet", PItext);

     // Write the DocumentType node.
     writer.WriteDocType("book", null , null, "<!ENTITY h \"hardcover\">");

     // Write a Comment node.
     writer.WriteComment("sample XML");

     // Write the root element.
     writer.WriteStartElement("book");

     // Write the genre attribute.
     writer.WriteAttributeString("genre", "novel");

     // Write the ISBN attribute.
     writer.WriteAttributeString("ISBN", "1-8630-014");

     // Write the title.
     writer.WriteElementString("title", "The Handmaid's Tale");

     // Write the style element.
     writer.WriteStartElement("style");
     writer.WriteEntityRef("h");
     writer.WriteEndElement();

     // Write the price.
     writer.WriteElementString("price", "19.95");

     // Write CDATA.
     writer.WriteCData("Prices 15% off!!");

     // Write the close tag for the root element.
     writer.WriteEndElement();

     writer.WriteEndDocument();

     // Write the XML to file and close the writer.
     writer.Flush();
     writer.Close();
  }
}

Option Strict
Option Explicit

Imports System.IO
Imports System.Xml

Public Class Sample
    Private Const filename As String = "sampledata.xml"
    
  Public Shared Sub Main()

     Dim settings As XmlWriterSettings = new XmlWriterSettings()
     settings.Indent = true
     Dim writer As XmlWriter = XmlWriter.Create(filename, settings)
        
     ' Write the Processing Instruction node.
     Dim PItext As String = "type=""text/xsl"" href=""book.xsl"""
     writer.WriteProcessingInstruction("xml-stylesheet", PItext)
        
     'Write the DocumentType node.
     writer.WriteDocType("book", Nothing, Nothing, "<!ENTITY h ""hardcover"">")
        
     ' Write a Comment node.
     writer.WriteComment("sample XML")
        
     ' Write the root element.
     writer.WriteStartElement("book")
        
     ' Write the genre attribute
     writer.WriteAttributeString("genre", "novel")
        
     ' Write the ISBN attribute.
     writer.WriteAttributeString("ISBN", "1-8630-014")
        
     ' Write the title.
     writer.WriteElementString("title", "The Handmaid's Tale")
        
     ' Write the style element.
     writer.WriteStartElement("style")
     writer.WriteEntityRef("h")
     writer.WriteEndElement()
       
     ' Write the price.
     writer.WriteElementString("price", "19.95")
        
     ' Write CDATA.
     writer.WriteCData("Prices 15% off!!")
        
     ' Write the close tag for the root element.
     writer.WriteEndElement()
        
     writer.WriteEndDocument()
        
     ' Write the XML to file and close the writer
     writer.Flush()
     writer.Close()
        
    End Sub
End Class

注解

此方法可用于 (而不是) WriteStartDocument 编写 XML 声明。 这可能会导致编码属性被错误写入。 例如，以下 C# 代码将导致无效的 XML 文档，因为默认编码为 UTF-8。

XmlWriter writer = XmlWriter.Create("output.xml");
writer.WriteProcessingInstruction("xml", "version='1.0' encoding='UTF-16'");
writer.WriteStartElement("root");
writer.Close();

如果 text 是 null 或 String.Empty，则此方法写入 ProcessingInstruction 没有数据内容的 ，例如 <？name？>。

如果文本包含无效的“？>”序列， XmlWriter 是否可以引发 ArgumentException (XmlTextWriter 对象) 或插入空格“？ >“以避免) 方法创建的Create对象写入无效的 XML XmlWriter (。

有关此方法的异步版本，请参阅 WriteProcessingInstructionAsync。