使用DataSet时遇到的问题

Question

我首先在项目名称 recvd.xsd 中手动创建了一个具有相应 recvd.xss 的 DataSet。在我的按钮单击事件中，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);
}

我收到的错误是

未将对象引用设置为对象的实例。

如果我从 SQL 查询中删除 as \"RECEIVED\" 并简单地执行 SQL 查询，则查询结果如下（根据用户输入而变化）

200200000452011 ……，n个12位数字。

请帮助我删除关于为什么我无法绑定到数据表的错误。

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 块，现在收到错误

Answer 1

尝试

SELECT case_no as `RECEIVED` ...

或者只是

SELECT case_no as RECEIVED ...

---

无论如何，正确的数据集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);
}

Answer 2

在你的 SQL 中，而不是 \"RECIEVED\" 你是否尝试过只 RECIEVED，没有引号？

Answer 3

您不需要在查询中使用“RECEIVED”，您可以像下面这样使用。

query = "SELECT case_no as [RECIEVED] from dcpanaji.Civil_t where dt_regis > '" + txtStartDate.Text + "' AND dt_regis < '" + txtEndDate.Text + "' AND court_no = " + DropDownList1.SelectedItem + "";

Answer 4

你可以像检查一样编写查询

query = "SELECT case_no as RECIEVED from dcpanaji.Civil_t where dt_regis > '" + txtStartDate.Text + "' AND dt_regis < '" + txtEndDate.Text + "' AND court_no = " + DropDownList1.SelectedItem + "";

......