WebClient.OpenWrite Method (String, String)


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Opens a stream for writing data to the specified resource, using the specified method.

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

Public Function OpenWrite (
	address As String,
	method As String
) As Stream


Type: System.String

The URI of the resource to receive the data.

Type: System.String

The method used to send the data to the resource. If null, the default is POST for http and STOR for ftp.

Return Value

Type: System.IO.Stream

A Stream used to write data to the resource.

Exception Condition

The address parameter is null.


The URI formed by combining BaseAddress, and address is invalid.


An error occurred while opening the stream.

The OpenWrite method returns a writable stream that is used to send data to a resource. The underlying request is made with the method specified in the method parameter. The data is sent to the server when you close the stream. This method blocks while opening the stream. To continue executing while waiting for the stream, use one of the OpenWriteAsync methods.

If the method parameter specifies a method that is not understood by the server, the underlying protocol classes determine what occurs. Typically, a WebException is thrown with the Status property set to indicate the error.

If the BaseAddress property is not an empty string ("") and address does not specify an absolute address, address must be a relative URI that is combined with BaseAddress to form the absolute URI of the requested data. If the QueryString property is not an empty string, it is appended to address.


This member outputs trace information when you enable network tracing in your application. For more information, see Network Tracing in the .NET Framework.

The following code example reads data from the command line and uses OpenWrite to obtain a stream used to write the data. Note that the Stream returned by OpenWrite must be closed to send the data.

Dim uriString As String
Console.Write(ControlChars.Cr + "Please enter the URI to post data to : ")
uriString = Console.ReadLine()
Console.WriteLine(ControlChars.Cr + "Please enter the data to be posted to the URI {0}:", uriString)
Dim postData As String = Console.ReadLine()
' Apply ASCII encoding to obtain an array of bytes.
Dim postArray As Byte() = Encoding.ASCII.GetBytes(postData)

' Create a new WebClient instance.
Dim myWebClient As New WebClient()

Console.WriteLine("Uploading to {0} ...", uriString)
Dim postStream As Stream = myWebClient.OpenWrite(uriString, "POST")

postStream.Write(postArray, 0, postArray.Length)

' Close the stream and release resources.

Console.WriteLine(ControlChars.Cr + "Successfully posted the data.")

.NET Framework
Available since 1.1
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