WebHeaderCollection.Add Method

Reference

Definition

Namespace:: System.Net

Assembly:: System.Net.WebHeaderCollection.dll

Assembly:: System.dll

Assembly:: netstandard.dll

Important

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Inserts a new header into the collection.

Overloads

Add(String)	Inserts the specified header into the collection.
Add(HttpRequestHeader, String)	Inserts the specified header with the specified value into the collection.
Add(HttpResponseHeader, String)	Inserts the specified header with the specified value into the collection.
Add(String, String)	Inserts a header with the specified name and value into the collection.

Add(String)

Source:: WebHeaderCollection.cs

Source:: WebHeaderCollection.cs

Source:: WebHeaderCollection.cs

Inserts the specified header into the collection.

public:
 void Add(System::String ^ header);

public void Add (string header);

override this.Add : string -> unit

Public Sub Add (header As String)

Parameters

header: String

The header to add, with the name and value separated by a colon.

Exceptions

ArgumentNullException

header is null or Empty.

ArgumentException

header does not contain a colon (:) character.

The length of value is greater than 65535.

-or-

The name part of header is Empty or contains invalid characters.

-or-

header is a restricted header that should be set with a property.

-or-

The value part of header contains invalid characters.

ArgumentOutOfRangeException

.NET Framework and .NET Core versions 2.0 - 3.1 only: The length of the string after the colon (:) is greater than 65535.

Examples

The following example adds a name/value pair to a WebHeaderCollection using the Add Method.

try
{
   //Create a web request for S"www.msn.com".
   HttpWebRequest^ myHttpWebRequest = dynamic_cast<HttpWebRequest^>(WebRequest::Create( "http://www.msn.com" ));

   //Get the headers associated with the request.
   WebHeaderCollection^ myWebHeaderCollection = myHttpWebRequest->Headers;
   Console::WriteLine( "Configuring Webrequest to accept Danish and English language using 'Add' method" );

   //Add the Accept-Language header (for Danish) in the request.
   myWebHeaderCollection->Add( "Accept-Language:da" );

   //Include English in the Accept-Langauge header.
   myWebHeaderCollection->Add( "Accept-Language:en;q=0.8" );

   //Get the associated response for the above request.
   HttpWebResponse^ myHttpWebResponse = dynamic_cast<HttpWebResponse^>(myHttpWebRequest->GetResponse());

   //Print the headers for the request.
   printHeaders( myWebHeaderCollection );
   myHttpWebResponse->Close();
}
//Catch exception if trying to add a restricted header.
catch ( ArgumentException^ e ) 
{
   Console::WriteLine( e->Message );
}
catch ( WebException^ e ) 
{
   Console::WriteLine( "\nWebException is thrown. \nMessage is : {0}", e->Message );
   if ( e->Status == WebExceptionStatus::ProtocolError )
   {
      Console::WriteLine( "Status Code : {0}", (dynamic_cast<HttpWebResponse^>(e->Response))->StatusCode );
      Console::WriteLine( "Status Description : {0}", (dynamic_cast<HttpWebResponse^>(e->Response))->StatusDescription );
      Console::WriteLine( "Server : {0}", (dynamic_cast<HttpWebResponse^>(e->Response))->Server );
   }
}
catch ( Exception^ e ) 
{
   Console::WriteLine( "Exception is thrown. Message is : {0}", e->Message );
}

try {
    //Create a web request for "www.msn.com".
    HttpWebRequest myHttpWebRequest = (HttpWebRequest) WebRequest.Create("http://www.msn.com");

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

    Console.WriteLine("Configuring Webrequest to accept Danish and English language using 'Add' method");

    //Add the Accept-Language header (for Danish) in the request.
    myWebHeaderCollection.Add("Accept-Language:da");

    //Include English in the Accept-Langauge header. 
    myWebHeaderCollection.Add("Accept-Language","en;q=0.8");

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

    //Print the headers for the request.
    printHeaders(myWebHeaderCollection);
    myHttpWebResponse.Close();
}
//Catch exception if trying to add a restricted header.
catch(ArgumentException e) {
    Console.WriteLine(e.Message);
}
catch(WebException e) {
    Console.WriteLine("\nWebException is thrown. \nMessage 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);
}

Public Shared Sub Main()

 Try
        'Create a web request for "www.msn.com".
        Dim myHttpWebRequest As HttpWebRequest = CType(WebRequest.Create("http://www.msn.com"), HttpWebRequest)
        
        'Get the headers associated with the request.
        Dim myWebHeaderCollection As WebHeaderCollection = myHttpWebRequest.Headers
        
    Console.WriteLine("Configuring Webrequest to accept Danish and English language using 'Add' method")
        
    'Add the Accept-Language header (for Danish) in the request.
        myWebHeaderCollection.Add("Accept-Language:da")
        
        'Include English in the Accept-Langauge header. 
        myWebHeaderCollection.Add("Accept-Language","en;q" + ChrW(61) + "0.8")
        
        'Get the associated response for the above request.
        Dim myHttpWebResponse As HttpWebResponse = CType(myHttpWebRequest.GetResponse(), HttpWebResponse)
        
        'Print the headers for the request.
        printHeaders(myWebHeaderCollection)
        myHttpWebResponse.Close()
    'Catch exception if trying to add a restricted header.
    Catch e As ArgumentException
        Console.WriteLine(e.Message)
    Catch e As WebException
        Console.WriteLine(e.Message)
        If e.Status = WebExceptionStatus.ProtocolError Then
            Console.WriteLine("Status Code : {0}", CType(e.Response, HttpWebResponse).StatusCode)
            Console.WriteLine("Status Description : {0}", CType(e.Response, HttpWebResponse).StatusDescription)
            Console.WriteLine("Server : {0}", CType(e.Response, HttpWebResponse).Server)
        End If
    Catch e As Exception
        Console.WriteLine(e.Message)
    End Try
End Sub

Note

The length of the value portion of header, that is, the string after the colon (:), is validated only in .NET Framework and .NET Core versions 2.0 - 3.1.

On all applicable .NET Framework versions: A WebHeaderCollection instance that's returned by the Headers property will throw an ArgumentOutOfRangeException if the length of the value portion of header is greater than 65535. All other WebHeaderCollection instances accept a value of any length.
On .NET Core versions through version 3.1: A WebHeaderCollection instance used with any header of type HttpResponseHeader will throw an ArgumentOutOfRangeException if the length of the value portion of header is greater than 65535. All other WebHeaderCollection instances accept a value of any length.
On .NET 5 and later versions: WebHeaderCollection accepts a value of any length.

Remarks

The header parameter must be specified in the format "name:value". If the specified header does not exist in the collection, a new header is added to the collection.

If the header specified in header is already present in the collection, the value part of the header is concatenated with the existing value.

Applies to

Add(HttpRequestHeader, String)

Source:: WebHeaderCollection.cs

Source:: WebHeaderCollection.cs

Source:: WebHeaderCollection.cs

Inserts the specified header with the specified value into the collection.

public:
 void Add(System::Net::HttpRequestHeader header, System::String ^ value);

public void Add (System.Net.HttpRequestHeader header, string? value);

public void Add (System.Net.HttpRequestHeader header, string value);

override this.Add : System.Net.HttpRequestHeader * string -> unit

Public Sub Add (header As HttpRequestHeader, value As String)

Parameters

header: HttpRequestHeader

The header to add to the collection.

value: String

The content of the header.

Exceptions

ArgumentOutOfRangeException

.NET Framework and .NET Core versions 2.0 - 3.1 only: The length of value is greater than 65535.

InvalidOperationException

This WebHeaderCollection instance does not allow instances of HttpRequestHeader.

Remarks

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

If the specified header is already present, value is added to the comma-separated list of values associated with the header.

Note

The length of value is validated only in .NET Framework and .NET Core versions 2.0 - 3.1.

On all applicable .NET Framework versions: A WebHeaderCollection instance that's returned by the Headers property will throw an ArgumentOutOfRangeException if the length of value is greater than 65535. All other WebHeaderCollection instances accept a value of any length.
On .NET Core versions through version 3.1: A WebHeaderCollection instance used with any header of type HttpResponseHeader will throw an ArgumentOutOfRangeException if the length of value is greater than 65535. All other WebHeaderCollection instances accept a value of any length.
On .NET 5 and later versions: WebHeaderCollection accepts a value of any length.

Applies to

Add(HttpResponseHeader, String)

Source:: WebHeaderCollection.cs

Source:: WebHeaderCollection.cs

Source:: WebHeaderCollection.cs

Inserts the specified header with the specified value into the collection.

public:
 void Add(System::Net::HttpResponseHeader header, System::String ^ value);

public void Add (System.Net.HttpResponseHeader header, string? value);

public void Add (System.Net.HttpResponseHeader header, string value);

override this.Add : System.Net.HttpResponseHeader * string -> unit

Public Sub Add (header As HttpResponseHeader, value As String)

Parameters

header: HttpResponseHeader

The header to add to the collection.

value: String

The content of the header.

Exceptions

ArgumentOutOfRangeException

.NET Framework and .NET Core versions 2.0 - 3.1 only: The length of value is greater than 65535.

InvalidOperationException

This WebHeaderCollection instance does not allow instances of HttpResponseHeader.

Remarks

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

If the specified header is already present, value is added to the comma-separated list of values associated with the header.

Note

The length of value is validated only in .NET Framework and .NET Core versions 2.0 - 3.1.

On all applicable .NET Framework versions: A WebHeaderCollection instance that's returned by the Headers property will throw an ArgumentOutOfRangeException if the length of value is greater than 65535. All other WebHeaderCollection instances accept a value of any length.
On .NET Core versions through version 3.1: A WebHeaderCollection instance used with any header of type HttpResponseHeader will throw an ArgumentOutOfRangeException if the length of value is greater than 65535. All other WebHeaderCollection instances accept a value of any length.
On .NET 5 and later versions: WebHeaderCollection accepts a value of any length.

Applies to

Add(String, String)

Source:: WebHeaderCollection.cs

Source:: WebHeaderCollection.cs

Source:: WebHeaderCollection.cs

Inserts a header with the specified name and value into the collection.

public:
 override void Add(System::String ^ name, System::String ^ value);

public override void Add (string name, string? value);

public override void Add (string name, string value);

override this.Add : string * string -> unit

Public Overrides Sub Add (name As String, value As String)

Parameters

name: String

The header to add to the collection.

value: String

The content of the header.

Exceptions

ArgumentException

name is null, Empty, or contains invalid characters.

-or-

name is a restricted header that must be set with a property setting.

-or-

value contains invalid characters.

ArgumentOutOfRangeException

.NET Framework and .NET Core versions 2.0 - 3.1 only: The length of value is greater than 65535.

Examples

The following example adds a name/value pair to a WebHeaderCollection using the Add Method.

try
{
   //Create a web request for S"www.msn.com".
   HttpWebRequest^ myHttpWebRequest = dynamic_cast<HttpWebRequest^>(WebRequest::Create( "http://www.msn.com" ));

   //Get the headers associated with the request.
   WebHeaderCollection^ myWebHeaderCollection = myHttpWebRequest->Headers;
   Console::WriteLine( "Configuring Webrequest to accept Danish and English language using 'Add' method" );

   //Add the Accept-Language header (for Danish) in the request.
   myWebHeaderCollection->Add( "Accept-Language:da" );

   //Include English in the Accept-Langauge header.
   myWebHeaderCollection->Add( "Accept-Language:en;q=0.8" );

   //Get the associated response for the above request.
   HttpWebResponse^ myHttpWebResponse = dynamic_cast<HttpWebResponse^>(myHttpWebRequest->GetResponse());

   //Print the headers for the request.
   printHeaders( myWebHeaderCollection );
   myHttpWebResponse->Close();
}
//Catch exception if trying to add a restricted header.
catch ( ArgumentException^ e ) 
{
   Console::WriteLine( e->Message );
}
catch ( WebException^ e ) 
{
   Console::WriteLine( "\nWebException is thrown. \nMessage is : {0}", e->Message );
   if ( e->Status == WebExceptionStatus::ProtocolError )
   {
      Console::WriteLine( "Status Code : {0}", (dynamic_cast<HttpWebResponse^>(e->Response))->StatusCode );
      Console::WriteLine( "Status Description : {0}", (dynamic_cast<HttpWebResponse^>(e->Response))->StatusDescription );
      Console::WriteLine( "Server : {0}", (dynamic_cast<HttpWebResponse^>(e->Response))->Server );
   }
}
catch ( Exception^ e ) 
{
   Console::WriteLine( "Exception is thrown. Message is : {0}", e->Message );
}

try {
    //Create a web request for "www.msn.com".
    HttpWebRequest myHttpWebRequest = (HttpWebRequest) WebRequest.Create("http://www.msn.com");

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

    Console.WriteLine("Configuring Webrequest to accept Danish and English language using 'Add' method");

    //Add the Accept-Language header (for Danish) in the request.
    myWebHeaderCollection.Add("Accept-Language:da");

    //Include English in the Accept-Langauge header. 
    myWebHeaderCollection.Add("Accept-Language","en;q=0.8");

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

    //Print the headers for the request.
    printHeaders(myWebHeaderCollection);
    myHttpWebResponse.Close();
}
//Catch exception if trying to add a restricted header.
catch(ArgumentException e) {
    Console.WriteLine(e.Message);
}
catch(WebException e) {
    Console.WriteLine("\nWebException is thrown. \nMessage 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);
}

Public Shared Sub Main()

 Try
        'Create a web request for "www.msn.com".
        Dim myHttpWebRequest As HttpWebRequest = CType(WebRequest.Create("http://www.msn.com"), HttpWebRequest)
        
        'Get the headers associated with the request.
        Dim myWebHeaderCollection As WebHeaderCollection = myHttpWebRequest.Headers
        
    Console.WriteLine("Configuring Webrequest to accept Danish and English language using 'Add' method")
        
    'Add the Accept-Language header (for Danish) in the request.
        myWebHeaderCollection.Add("Accept-Language:da")
        
        'Include English in the Accept-Langauge header. 
        myWebHeaderCollection.Add("Accept-Language","en;q" + ChrW(61) + "0.8")
        
        'Get the associated response for the above request.
        Dim myHttpWebResponse As HttpWebResponse = CType(myHttpWebRequest.GetResponse(), HttpWebResponse)
        
        'Print the headers for the request.
        printHeaders(myWebHeaderCollection)
        myHttpWebResponse.Close()
    'Catch exception if trying to add a restricted header.
    Catch e As ArgumentException
        Console.WriteLine(e.Message)
    Catch e As WebException
        Console.WriteLine(e.Message)
        If e.Status = WebExceptionStatus.ProtocolError Then
            Console.WriteLine("Status Code : {0}", CType(e.Response, HttpWebResponse).StatusCode)
            Console.WriteLine("Status Description : {0}", CType(e.Response, HttpWebResponse).StatusDescription)
            Console.WriteLine("Server : {0}", CType(e.Response, HttpWebResponse).Server)
        End If
    Catch e As Exception
        Console.WriteLine(e.Message)
    End Try
End Sub

Note

The length of value is validated only in .NET Framework and .NET Core versions 2.0 - 3.1.

On all applicable .NET Framework versions: A WebHeaderCollection instance that's returned by the Headers property will throw an ArgumentOutOfRangeException if the length of value is greater than 65535. All other WebHeaderCollection instances accept a value of any length.
On .NET Core versions through version 3.1: A WebHeaderCollection instance used with any header of type HttpResponseHeader will throw an ArgumentOutOfRangeException if the length of value is greater than 65535. All other WebHeaderCollection instances accept a value of any length.
On .NET 5 and later versions: WebHeaderCollection accepts a value of any length.

Remarks

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

If the header specified in name is already present, value is added to the existing comma-separated list of values associated with name.

Applies to

Share via

WebHeaderCollection.Add Method

Definition

Overloads

Add(String)

Parameters

Exceptions

Examples

Remarks

Applies to

Add(HttpRequestHeader, String)

Parameters

Exceptions

Remarks

Applies to

Add(HttpResponseHeader, String)

Parameters

Exceptions

Remarks

Applies to

Add(String, String)

Parameters

Exceptions

Examples

Remarks

Applies to

Additional resources