ReadValueChunkAsync Method
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XmlReader.ReadValueChunkAsync Method (Char[], Int32, Int32)

.NET Framework 4.6 and 4.5

Asynchronously reads large streams of text embedded in an XML document.

Namespace:   System.Xml
Assembly:  System.Xml (in System.Xml.dll)

public virtual Task<int> ReadValueChunkAsync(
	char[] buffer,
	int index,
	int count


Type: System.Char[]

The array of characters that serves as the buffer to which the text contents are written. This value cannot be null.

Type: System.Int32

The offset within the buffer where the XmlReader can start to copy the results.

Type: System.Int32

The maximum number of characters to copy into the buffer. The actual number of characters copied is returned from this method.

Return Value

Type: System.Threading.Tasks.Task<Int32>

The number of characters read into the buffer. The value zero is returned when there is no more text content.

Exception Condition

An XmlReader method was called before a previous asynchronous operation finished. In this case, InvalidOperationException is thrown with the message “An asynchronous operation is already in progress.”


An XmlReader asynchronous method was called without setting the Async flag to true. In this case, InvalidOperationException is thrown with the message “Set XmlReaderSettings.Async to true if you want to use Async Methods.”

This is the asynchronous version of ReadValueChunk, with the same functionality. To use this method, you must set the Async flag to true.

Universal Windows Platform
Available since 4.5
.NET Framework
Available since 4.5
Portable Class Library
Supported in: portable .NET platforms
Windows Phone Silverlight
Available since 8.0
Windows Phone
Available since 8.1
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