如何在选择项值之前加载sql数据源

本文关键字：加载 sql 数据源 选择 | 更新日期: 2023-09-27 18:29:25

我的asp.net页面上有SQL数据源，当页面加载时出现此错误

"ddlTypes"的SelectedValue无效，因为它不在项列表中。参数名称：值

private void GetQueryString(Uri tempUri)
{
    if (HttpUtility.ParseQueryString(tempUri.Query).Get("IntrestFocus") != null)
    {
        ddlTopics.SelectedValue = HttpUtility.ParseQueryString(tempUri.Query).Get("IntrestFocus"); 
    }
    else
        if (HttpUtility.ParseQueryString(tempUri.Query).Get("Skills") != null)
        {
            ddlSkills.SelectedValue = HttpUtility.ParseQueryString(tempUri.Query).Get("Skills"); 
        }
    else
        if(HttpUtility.ParseQueryString(tempUri.Query).Get("Type") != null)
        {
            ddlTypes.SelectedValue = HttpUtility.ParseQueryString(tempUri.Query).Get("Type"); 
        }
}
<asp:SqlDataSource ID="SqlDSTypes" runat="server" ConnectionString="<%$ ConnectionStrings:SiteSqlServer %>" SelectCommand="SELECT * FROM [Types]"></asp:SqlDataSource>

                <asp:DropDownList CssClass="selectpicker mobile-stack select-type" data-style="lts-white font-black drop-shadow select-height" ID="ddlTypes" runat="server" DataSourceID="SqlDSTypes" DataTextField="Description" DataValueField="Id" AppendDataBoundItems="True" ClientIDMode="Static">
                    <asp:ListItem Value="0">Select a Type</asp:ListItem>
                </asp:DropDownList>

如何在选择项值之前加载sql数据源

这是您的主要选项：

private void GetQueryString(Uri tempUri)
{
  ddlTopics.DataSource = SqlDSTypes.Select(DataSourceSelectArguments.Empty);
  ddlTopics.DataBind();
  //Put your logic here, behind databind ...
  if (HttpUtility.ParseQueryString(tempUri.Query).Get("IntrestFocus") != null)
  {
      ddlTopics.SelectedValue = HttpUtility.ParseQueryString(tempUri.Query).Get("IntrestFocus"); 
  }
  else
      if (HttpUtility.ParseQueryString(tempUri.Query).Get("Skills") != null)
      {
        ddlSkills.SelectedValue = HttpUtility.ParseQueryString(tempUri.Query).Get("Skills"); 
      }
  else
      if(HttpUtility.ParseQueryString(tempUri.Query).Get("Type") != null)
      {
        ddlTypes.SelectedValue = HttpUtility.ParseQueryString(tempUri.Query).Get("Type"); 
      }
}

当您选择上面的答案时，还要确保没有设置DataSourceID。

然而，还有另一种可能性，那就是使用OnDataBound事件并将DropDownList逻辑放入其中。它将在DropDownList数据绑定后被激发，然后：

你的代码背后：

protected function ddlTopics_DataBound(Object sender, EventArgs e)
{
  //Put your logic here, behind databind ...
  if (HttpUtility.ParseQueryString(tempUri.Query).Get("IntrestFocus") != null)
  {
      ddlTopics.SelectedValue = HttpUtility.ParseQueryString(tempUri.Query).Get("IntrestFocus"); 
  }
  else
      if (HttpUtility.ParseQueryString(tempUri.Query).Get("Skills") != null)
      {
        ddlSkills.SelectedValue = HttpUtility.ParseQueryString(tempUri.Query).Get("Skills"); 
      }
  else
      if(HttpUtility.ParseQueryString(tempUri.Query).Get("Type") != null)
      {
        ddlTypes.SelectedValue = HttpUtility.ParseQueryString(tempUri.Query).Get("Type"); 
      }  
}

您的aspx:

<asp:DropDownList ID="ddlTopics" OnDataBound="ddlTopics_DataBound" runat="server" ...

后者可能是最简洁的选择。

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