尝试 DropDownList.SelectedIndex属性 [ ^ ] - 应该是一个盯着选定的指南更改。

Try DropDownList.SelectedIndex Property [^] - should be a guide to get stared with selected change.

下面的代码需要写在下拉列表的selectedindexchanged事件中。

The below code needs to be written in the selectedindexchanged event of the dropdown.

ComboBox cmb = (ComboBox)sender;
if (cmb.SelectedValue.ToString().Equals("Something")
{
    //Do Something
}

希望这会有所帮助。

Hope this helps.

基于这个事实TS提到填充数据库的下拉列表，SelectedValue实际上不太可能是一个字符串。

很可能，ValueMember绑定到数据库中记录的Id，DisplayMember必然会一些说明。

Based on the fact that the TS mentioned populating the dropdown from the database, it's very unlikely that SelectedValue is actually a string.
More than likely, ValueMember is bound to the Id of the record in the database, DisplayMember is bound to some Description.

object val = ((ComboBox)sender).SelectedValue; // returns the Id
string txt = ((ComboBox)sender).SelectedText; // returns the text visible on the screen for the selected item
object item = ((ComboBox)sender).SelectedItem; // returns the entire object from the datasource you have bound to the combobox

根据您的需要，使用其中任何一个来检索/显示更多数据。

Depending on your needs, use any of these to retrieve/show further data.