如何将默认值设置为下拉列表控件？

Question

我的网页上有一个下拉列表控件.我已将数据表绑定到dropdownlist控件,如下所示 -

lstDepartment.DataTextField = "DepartmentName";
    lstDepartment.DataValueField = "DepartmentID";
    lstDepartment.DataSource = dtDept;
    lstDepartment.DataBind();

在页面加载事件中,我想从我的其他表字段中将默认值设置为下拉列表控件.

这该怎么做？

Answer 1

在你之后DataBind():

lstDepartment.SelectedIndex = 0;  //first item

or

lstDepartment.SelectedValue = "Yourvalue"

or 
//add error checking, just an example, FindByValue may return null
lstDepartment.Items.FindByValue("Yourvalue").Selected = true;

or
//add error checking, just an example, FindByText may return null
lstDepartment.Items.FindByText("Yourvalue").Selected = true;

Answer 2

如果您知道默认值项的索引，只需

lstDepartment.SelectedIndex = 1;//the second item

或者如果您知道要设置的值，只需

lstDepartment.SelectedValue = "the value you want to set";

Answer 3

假设另一个表中的 DropDownList 控件也包含 DepartmentName 和 DepartmentID：

lstDepartment.ClearSelection();

foreach (var item in lstDepartment.Items) 
{
  if (item.Value == otherDropDownList.SelectedValue)
  {
    item.Selected = true;
  }
}