我做的一个东西，需要gatagridview根据combox内容改变而改变，我写了一下代码，调试的时候总是说使用了未赋值的selectCmd，烦劳各位大侠给看看是怎么回事，感激不尽！
                  private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            string connStr, selectCmd;
            connStr = "Provider=Microsoft.Jet.OLEDB.4.0;";
            connStr += @"Data Source=E:\保障设备2003.mdb";
            if (comboBox1.Text == "1")
            {
                selectCmd = "Select * From 保障设备分类总汇 where 所属目录='s1'";
            }
            else if (comboBox1.Text == " 2")
            {
                selectCmd = "Select * From 保障设备分类总汇 where 所属目录='s2'";
            }
            OleDbConnection conn;
            OleDbDataAdapter myAdapter;
            DataSet myDataSet = new DataSet();
            conn = new OleDbConnection(connStr);
            conn.Open();
            myAdapter = new OleDbDataAdapter(selectCmd, conn);
            myAdapter.Fill(myDataSet, "保障设备2003");
            dataGridView1.DataSource = myDataSet.Tables["保障设备2003"];
        }


问题解决了！string connStr, selectCmd;改成string connStr, selectCmd=null;就成了！
感谢各位！

[ 本帖最后由 jtzcc 于 2010-9-12 22:16 编辑 ]