WebHeaderCollection.Add Method (String)
Inserts the specified header into the collection.
Assembly: System (in System.dll)
header is null or Empty.
header does not contain a colon (:) character.
The length of value is greater than 65535.
The name part of header is Empty or contains invalid characters.
header is a restricted header that should be set with a property.
The value part of header contains invalid characters.
The length the string after the colon (:) is greater than 65535.
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.
Available since 1.1