问号查询参数？(Question Mark as Query Parameter?)

我在当一个DataSource样品跌跌撞撞http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.querystringparameter(v=vs.100).aspx

该代码是如下

<%@Page  Language="C#" %>
<%@Import Namespace="System.Data" %>
<%@Import Namespace="System.Data.Common" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<script runat="server">
private void UpdateRecords(Object source, EventArgs e)
{
  // This method is an example of batch updating using a
  // data source control. The method iterates through the rows
  // of the GridView, extracts each CheckBox from the row and, if
  // the CheckBox is checked, updates data by calling the Update
  // method of the data source control, adding required parameters
  // to the UpdateParameters collection.
  CheckBox cb;
  foreach(GridViewRow row in this.GridView1.Rows) {
    cb = (CheckBox) row.Cells[0].Controls[1];
    if(cb.Checked) {
      string oid = (string) row.Cells[1].Text;
      MyAccessDataSource.UpdateParameters.Add(new Parameter("date",TypeCode.DateTime,DateTime.Now.ToString()));
      MyAccessDataSource.UpdateParameters.Add(new Parameter("orderid",TypeCode.String,oid));
      MyAccessDataSource.Update();
      MyAccessDataSource.UpdateParameters.Clear();
    }
  }
}
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
  <head runat="server">
    <title>ASP.NET Example</title>
</head>
<body>
    <form id="form1" runat="server">

<!-- Security Note: The SqlDataSource uses a QueryStringParameter,
     Security Note: which does not perform validation of input from the client.
     Security Note: To validate the value of the QueryStringParameter, handle the Selecting event. -->

      <asp:SqlDataSource
        id="MyAccessDataSource"
        runat="server"
        ProviderName="<%$ ConnectionStrings:MyPasswordProtectedAccess.providerName%>"
        ConnectionString="<%$ ConnectionStrings:MyPasswordProtectedAccess%>"
        SelectCommand="SELECT OrderID, OrderDate, RequiredDate, ShippedDate FROM Orders WHERE EmployeeID=?"
        UpdateCommand="UPDATE Orders SET ShippedDate=? WHERE OrderID = ?">
        <SelectParameters>
          <asp:QueryStringParameter Name="empId" QueryStringField="empId" />
        </SelectParameters>
      </asp:SqlDataSource>

      <asp:GridView
        id ="GridView1"
        runat="server"
        DataSourceID="MyAccessDataSource"
        AllowPaging="True"
        PageSize="10"
        AutoGenerateColumns="False">
          <columns>
            <asp:TemplateField HeaderText="">
              <ItemTemplate>
                <asp:CheckBox runat="server" />
              </ItemTemplate>
            </asp:TemplateField>
            <asp:BoundField HeaderText="Order" DataField="OrderID" />
            <asp:BoundField HeaderText="Order Date" DataField="OrderDate" />
            <asp:BoundField HeaderText="Required Date" DataField="RequiredDate" />
            <asp:BoundField HeaderText="Shipped Date" DataField="ShippedDate" />
          </columns>
      </asp:GridView>

      <asp:Button
        id="Button1"
        runat="server"
        Text="Update the Selected Records As Shipped"
        OnClick="UpdateRecords" />

      <asp:Label id="Label1" runat="server" />

    </form>
  </body>
</html>

我曾尝试这个代码。但是，服务器返回

不正确的语法附近的“？”。 说明：在当前Web请求的执行过程中发生未处理的异常。 请检查堆栈跟踪有关该错误它起源于代码的详细信息和。 异常详细信息：System.Data.SqlClient.SqlException：附近有语法错误“？”。

什么做EmployeeID=? ， ShippedDate=? 和OrderID = ? 在指定SelectCommand和UpdateCommand ？他们是否正确写入？

如何使此代码的工作？

Answer 1:

一些数据库系统使用匿名参数，通常由一个信号? 。然后，您必须提供正确顺序的参数。

其他系统使用命名参数。 SqlServer的使用@name语法。然后，您可以提供的参数失灵，因为它们在名称，而不是位置一致。

更改WHERE EmployeeID=? 到WHERE EmployeeID=@empId以配合您的参数的名称。

Answer 2:

这三个参数应改为

EmployeeID = @empId
ShippedDate = @date
OrderID = @ordered

MSDN的样品，有时不工作。