ADO.NET查询语句总是报错为什么？在线等，挺急的

Question

string SQL="SELECT * FROM MobileBrand";

            DataTable dt=new DataTable();

            SqlDataAdapter adapter = new SqlDataAdapter(SQL,ConStr);

            adapter.Fill(dt);

            this.cboBrand.DisplayMember="Brand";

            this.cboBrand.ValueMember="BrandID";

            this.cboBrand.DataSource = dt;