XceedEncryptionLib.XceedSigning signer = new XceedEncryptionLib.XceedSigningClass();

signer.License( @"your license key" );      

try
{
  XceedEncryptionLib.XceedRSASigningMethod rsa = new XceedEncryptionLib.XceedRSASigningMethodClass(); 

  // The following call to SetRandomKeyPair would, in the real world,
  // be replaced by the assignment of a Private Key to the PrivateKey property.
  object seed = null;

  rsa.SetRandomKeyPair( 512, ref seed ); 

  // Set the signing method type
  signer.SigningMethod = rsa; 

  object source = "This is the data to sign";
  signer.Sign( ref source, true ); 

  // Fetch the signature
  object signature = rsa.get_Signature(); 

  // Verify the signature
  signer.Verify( ref source, true );
}
catch( System.Runtime.InteropServices.COMException except )
{
  MessageBox.Show( except.ToString() );
}