它的数据源

本文关键字：数据源 | 更新日期: 2023-09-27 17:50:28

大家好，我有关于下拉列表的问题。我使用下拉列表与数据源。我怎样才能得到我选择的值?

// I need a if statement here because my programme doesn't know which value of dropdown list selected and I don't know how to use this with datasource.
if(//if I select quiz 1 from dropdown list ,quiz 1 should list questions.)
SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["RegConnectionString"].ConnectionString);
string chooce = "Select Quiz from tblQuiz where Quiz=1 ";
SqlCommand userExist = new SqlCommand(chooce, con);
con.Open();
int temp = Convert.ToInt32(userExist.ExecuteScalar().ToString());
if (temp == 1)
{
    if (rbList.Items[0].Selected == true)
    {
        string cmdStr = "Select Question from tblQuiz where ID=1";
        SqlCommand quest = new SqlCommand(cmdStr, con);
        lblque.Text = quest.ExecuteScalar().ToString();
        con.Close();
    }

它的数据源

您可以使用List, Dictionary, Enum, DataSet DataTable以不同的方式绑定下拉列表。
在绑定下拉菜单的数据源时，你必须考虑三件事:

  1. DataSource -数据集或数据表或数据源的名称
  2. DataValueField -这些字段将被隐藏
  3. DataTextField -这些字段将显示在dropwon上。

您可以使用以下代码将下拉列表绑定到数据源作为datatable:

  SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnString"].ConnectionString);
    SqlCommand cmd = new SqlCommand("Select * from tblQuiz", con);
    SqlDataAdapter da = new SqlDataAdapter(cmd);
    DataTable dt=new DataTable();
    da.Fill(dt);
    DropDownList1.DataTextField = "QUIZ_Name";
    DropDownList1.DataValueField = "QUIZ_ID"
    DropDownList1.DataSource = dt;
    DropDownList1.DataBind();

如果你想处理下拉列表的选择，那么你必须改变AutoPostBack="true"，你可以使用SelectedIndexChanged事件来写你的代码。

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
    string strQUIZ_ID=DropDownList1.SelectedValue;
    string strQUIZ_Name=DropDownList1.SelectedItem.Text;
    // Your code..............
}

protected void Page_Load(object sender, EventArgs e)
{
    if (!Page.IsPostBack)
    {
        drpCategory.DataSource = CategoryHelper.Categories;
        drpCategory.DataTextField = "Name";
        drpCategory.DataValueField = "Id";
        drpCategory.DataBind();
    }
}

参考此链接中的示例。这可能对你有帮助。

http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.dropdownlist.aspx 

void Page_Load(Object sender, EventArgs e)
  {
     // Load data for the DropDownList control only once, when the 
     // page is first loaded.
     if(!IsPostBack)
     {
        // Specify the data source and field names for the Text 
        // and Value properties of the items (ListItem objects) 
        // in the DropDownList control.
        ColorList.DataSource = CreateDataSource();
        ColorList.DataTextField = "ColorTextField";
        ColorList.DataValueField = "ColorValueField";
        // Bind the data to the control.
        ColorList.DataBind();
        // Set the default selected item, if desired.
        ColorList.SelectedIndex = 0;
     }
  }
void Selection_Change(Object sender, EventArgs e)
  {
     // Set the background color for days in the Calendar control
     // based on the value selected by the user from the 
     // DropDownList control.
     Calendar1.DayStyle.BackColor = 
         System.Drawing.Color.FromName(ColorList.SelectedItem.Value);
  }

这取决于您如何设置下拉菜单的默认值。使用选定值，但必须设置选定值。例如，我用表/列表的name和id字段填充数据源。我将所选值设置为id字段，并将显示设置为名称。当我选择时，我得到id字段。我使用它来搜索关系表并查找实体/记录。

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