c# - 使用数据集的问题

Question

我首先在我的项目名称 recvd.xsd 中手动创建了一个 DataSet 并具有相应的 recvd.xss。在我的按钮点击事件中，我完成了以下编码。

try 
{
    DataSet recvd_REPORT = new DataSet();
    DataTable REPORT = new DataTable();
    String dd_webCofig = ConfigurationManager.ConnectionStrings["server2"].ConnectionString;
    OdbcConnection ddlistconn = new OdbcConnection(dd_webCofig);
    ddlistconn.Open();

    REPORT = recvd_REPORT.Tables["REPORT"];
    DataColumn myDataColumn = new DataColumn();
    myDataColumn.DataType = typeof(System.Int32);
    myDataColumn.ColumnName = "RECEIVED";
    myDataColumn.ReadOnly = false;
    myDataColumn.Unique = false;
    // Add the Column to the DataColumnCollection.
    REPORT.Columns.Add(myDataColumn);

    string query = "SELECT case_no as \"RECEIVED\" from dcpanaji.Civil_t where dt_regis > '" + txtStartDate.Text + "' AND dt_regis < '" + txtEndDate.Text + "' AND court_no = " + DropDownList1.SelectedItem + "";
    Response.Write(query);
    OdbcCommand cmd = new OdbcCommand(query, ddlistconn);
    OdbcDataReader loginMyReader = cmd.ExecuteReader();

    OdbcDataAdapter adptr = new OdbcDataAdapter(query, ddlistconn);
    adptr.Fill(REPORT);

    ddlistconn.Close();   
}
catch (Exception ex)
{
    Response.Write(ex.Message);
}

我得到的错误是

Object reference not set to an instance of an object.

如果我从我的 SQL 查询中删除 as\"RECEIVED\" 并简单地执行我的 SQL 查询，那么我的查询结果如下(因用户输入而异)

200200000452011 ......，n个12位数字。

请帮助我消除关于为什么我无法绑定(bind)到 DataTable 的错误。

我在执行 Response.Write(query); 之前收到错误，为什么会出现这个问题？

我删除了 try catch block ，现在我得到了错误

Answer 1

尝试

SELECT case_no as `RECEIVED` ...

或者只是

SELECT case_no as RECEIVED ...

---

无论如何，正确的 DataSet 填充代码应该如下所示:

DataSet ds = new DataSet();
using (OdbcConnection connection = new OdbcConnection(connectionString))
using (OdbcCommand command = new OdbcCommand(sqlQuery, connection)
using (OdbcDataAdapter adapter = new OdbcDataAdapter(command)
{
    adapter.Fill(ds);
}