To solver first error use
int c=(int)MAcmd.ExecuteScalar();
instead of
int c=MAcmd.ExecuteScalar();
And second error is
Label1.Text + "record already exits";
you are missing a "=" operator. Use this
Label1.Text += "record already exits";
OR
Label1.Text = "record already exits";
And it is a compile time error, so it would show a red line under it.
Don't why you cant figure out these simple error.s