XmlTextReader.HasValue Property

Reference

Definition

Namespace:: System.Xml

Assemblies:: netstandard.dll, System.Xml.ReaderWriter.dll

Assembly:: System.Xml.ReaderWriter.dll

Assembly:: System.Xml.dll

Assembly:: netstandard.dll

Source:: XmlTextReader.cs

Source:: XmlTextReader.cs

Source:: XmlTextReader.cs

Important

Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.

Gets a value indicating whether the current node can have a Value other than String.Empty.

public:
 virtual property bool HasValue { bool get(); };

public override bool HasValue { get; }

member this.HasValue : bool

Public Overrides ReadOnly Property HasValue As Boolean

Property Value

Boolean

true if the node on which the reader is currently positioned can have a Value; otherwise, false.

Examples

The following example displays the value for every node that can have a value.

#using <System.Xml.dll>

using namespace System;
using namespace System::IO;
using namespace System::Xml;
int main()
{
   XmlTextReader^ reader = nullptr;
   try
   {
      
      //Load the reader with the XML file.
      reader = gcnew XmlTextReader( "book1.xml" );
      reader->WhitespaceHandling = WhitespaceHandling::None;
      
      //Parse the file and display each node.
      while ( reader->Read() )
      {
         if ( reader->HasValue )
                  Console::WriteLine( "({0})  {1}={2}", reader->NodeType, reader->Name, reader->Value );
         else
                  Console::WriteLine( "({0}) {1}", reader->NodeType, reader->Name );
      }
   }
   finally
   {
      if ( reader != nullptr )
            reader->Close();
   }

}

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

public class Sample
{

  public static void Main()
  {
    XmlTextReader reader = null;

    try
    {
        //Load the reader with the XML file.
        reader = new XmlTextReader("book1.xml");
        reader.WhitespaceHandling = WhitespaceHandling.None;

        //Parse the file and display each node.
        while (reader.Read())
        {
           if (reader.HasValue)
             Console.WriteLine("({0})  {1}={2}", reader.NodeType, reader.Name, reader.Value);
           else
             Console.WriteLine("({0}) {1}", reader.NodeType, reader.Name);
         }
     }

     finally
     {
       if (reader!=null)
         reader.Close();
     }
  }
} // End class

Imports System.IO
Imports System.Xml

Public Class Sample
    
    Public Shared Sub Main()
        Dim reader As XmlTextReader = Nothing
        
        Try
            'Load the reader with the XML file.
            reader = New XmlTextReader("book1.xml")
            reader.WhitespaceHandling = WhitespaceHandling.None
            
            'Parse the file and display each node.
            While reader.Read()
                If reader.HasValue Then
                    Console.WriteLine("({0})  {1}={2}", reader.NodeType, reader.Name, reader.Value)
                Else
                    Console.WriteLine("({0}) {1}", reader.NodeType, reader.Name)
                End If
            End While
        
        Finally
            If Not (reader Is Nothing) Then
                reader.Close()
            End If
        End Try
    End Sub
End Class

The example uses the file, book1.xml, as input.

XML


<?xml version='1.0' ?>
<!DOCTYPE book [<!ENTITY h 'hardcover'>]>
<book>
  <title>Pride And Prejudice</title>
  <misc>&h;</misc>
</book>

Remarks

Бележка

Starting with the .NET Framework 2.0, we recommend that you create XmlReader instances by using the XmlReader.Create method to take advantage of new functionality.

The following table lists node types that have a value to return.

Node type	Value
`Attribute`	The value of the attribute.
`CDATA`	The content of the CDATA section.
`Comment`	The content of the comment.
`DocumentType`	The internal subset.
`ProcessingInstruction`	The entire content, excluding the target.
`SignificantWhitespace`	The white space between markup in a mixed content model.
`Text`	The content of the text node.
`Whitespace`	The white space between markup.
`XmlDeclaration`	The content of the declaration.

Applies to

Продукт	Версии
.NET	Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9, 10
.NET Framework	1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard	2.0, 2.1

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