int newsid = Convert.ToInt32(Request.QueryString.Get("ID")); 

string strUpdate = "UPDATE TbNews SET StNewsName= @StNewsName ,  StNewsSummary = @StNewsSummary , StNewsDescription= @StNewsDescription WHERE InNewsId = @InNewsId";

SqlConnection sqlconn = new SqlConnection(...);
SqlCommand cmdguncelle = new SqlCommand(strUpdate, sqlconn);

cmdguncelle.Parameters.AddWithValue( "@StNewsName", TextBox1.Text );
cmdguncelle.Parameters.AddWithValue( "@StNewsSummary", TextBox2.Text );
cmdguncelle.Parameters.AddWithValue( "@StNewsDescription", TextBox3.Text );
cmdguncelle.Parameters.AddWithValue( "@InNewsId", newsid );

try
{
cmdguncelle.Connection.Open();
cmdguncelle.ExecuteNonQuery();
}
catch (SqlException ex)
{
// Hatalar (ErrorLabel.Text = "Error: " + ex.Message;)

}
finally
{
cmdguncelle.Connection.Close();
}