a problem with SqlDataAdapter

string connection = "Server=NIMIS\\TEST;database=Projects;integrated security=true";
string query="UPDATE fest SET nwem='6' WHERE num='20'";
SqlConnection mycon = new SqlConnection(connection);
SqlDataAdapter mydaap = new SqlDataAdapter("select * from  fest", mycon);
SqlCommand up = new SqlCommand(query, mycon);
DataSet myset = new DataSet();
mydaap.Fill(myset, "fest");
mydaap.UpdateCommand = up;
mydaap.Update(myset, "fest");