WebClient.OpenWrite Method (String)


Opens a stream for writing data to the specified resource.

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

Public Function OpenWrite (
	address As String
) As Stream


Type: System.String

The URI of the resource to receive the data.

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. This method blocks while opening the stream. To continue executing while waiting for the stream, use one of the OpenWriteAsync methods.

If the BaseAddress property is not an empty string ("") and address does not contain an absolute URI, 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 method uses the STOR command to upload an FTP resource. For an HTTP resource, the POST method is used.


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 for writing the data. Note that the Stream returned by OpenWrite is closed after the data is sent.

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)

' OpenWrite implicitly sets HTTP POST as the request method.
Dim postStream As Stream = myWebClient.OpenWrite(uriString)
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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