填充下拉列表控件以及“请选择一个值”选项
我正在从数据库填充下拉列表控件。然而，当我在运行时显示下拉菜单时，我希望第一个可见选项是“请选择一名教职人员”（这将是选项值 0）。 我怎样才能做到这一点？
SqlConnection con = new SqlConnection(strConn);
string sqlFacultyMember = "usp_GetFacultyMember";
SqlCommand cmdFacultyMember = new SqlCommand(sqlFacultyMember, con);
cmdFacultyMember.CommandType = CommandType.StoredProcedure;
con.Open();
SqlDataAdapter ada = new SqlDataAdapter(cmdFacultyMember);
DataSet ds = new DataSet();
ada.Fill(ds);
ddlFacultyMember.DataSource = ds;
ddlFacultyMember.DataValueField = "UserID";
ddlFacultyMember.DataTextField = "FullName";
ddlFacultyMember.DataBind();
I am populating a dropdownlist control from a database. That happes fine, however, when I display the dropdown at runtime, I want the first visible option to be "Please select a faculty member" (which would be option value 0).
How can I accomplish that?
SqlConnection con = new SqlConnection(strConn);
string sqlFacultyMember = "usp_GetFacultyMember";
SqlCommand cmdFacultyMember = new SqlCommand(sqlFacultyMember, con);
cmdFacultyMember.CommandType = CommandType.StoredProcedure;
con.Open();
SqlDataAdapter ada = new SqlDataAdapter(cmdFacultyMember);
DataSet ds = new DataSet();
ada.Fill(ds);
ddlFacultyMember.DataSource = ds;
ddlFacultyMember.DataValueField = "UserID";
ddlFacultyMember.DataTextField = "FullName";
ddlFacultyMember.DataBind();
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您还可以在绑定后将项目添加到 DropDownList，如下所示：
我喜欢这种方法的一点是，它将添加到 UI 中，我认为它属于 UI，因为这对用户来说是一种方便，而不是您真正想要对其采取行动的数据。
You can also add the item to the DropDownList after you bind it like so:
What I like about this approach is it leaves the adding of this to the UI, where I think it belongs, since this is a convenience for the user, not a piece of data you actually want to action on.
您需要在
DataSet中的位置 0 处插入一条记录，其中Value = "0"和Text = "Please Select a Value"。You need to insert a record at position 0 in the
DataSetwithValue = "0"andText = "Please Select a Value".您需要设置 AppendDataBoundItems 设置为 true。另外，在您的 SelectionIndexChanged 事件中检查所选索引是否不为零。
You need to set the AppendDataBoundItems to true for your DropDownList. Also in your selectionindexchanged event check if the selected index is not zero.