This documentation is archived and is not being maintained.

WebHeaderCollection.Set Method (String, String)

Sets the specified header to the specified value.

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

public override void Set(
	string name,
	string value


Type: System.String
The header to set.
Type: System.String
The content of the header to set.


name is null or Empty.


The length of value is greater than 65535.


name is a restricted header.


name or value contain invalid characters.

If the header specified in the header does not exist, the Set method inserts a new header into the list of header name/value pairs.

If the header specified in header is already present, value replaces the existing value.

The following example uses the Set method to set the value of an existing header.

		try {
			// Create a web request for "".
		 	HttpWebRequest myHttpWebRequest = (HttpWebRequest) WebRequest.Create("");

			// Get the headers associated with the request.
			WebHeaderCollection myWebHeaderCollection = myHttpWebRequest.Headers;

			// Set the Cache-Control header in the request.
			myWebHeaderCollection.Set("Cache-Control", "no-cache");

			// Get the associated response for the above request.
		 	HttpWebResponse myHttpWebResponse = (HttpWebResponse) myHttpWebRequest.GetResponse();

			Console.WriteLine ("Headers after 'Set' method is used on Cache-Control :");
			// Print the headers for the request.
		// Catch exception if trying to set a restricted header.
		catch(ArgumentException e) {
			Console.WriteLine("ArgumentException is thrown. Message is :" + e.Message);
		catch(WebException e) {
			Console.WriteLine("WebException is thrown. Message is :" + e.Message);
			if(e.Status == WebExceptionStatus.ProtocolError) {
				Console.WriteLine("Status Code : {0}", ((HttpWebResponse)e.Response).StatusCode);
				Console.WriteLine("Status Description : {0}", ((HttpWebResponse)e.Response).StatusDescription);
				Console.WriteLine("Server : {0}", ((HttpWebResponse)e.Response).Server);
		catch(Exception e) {
			Console.WriteLine("Exception is thrown. Message is :" + e.Message);

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.