How to bind a list of items in a dropdownlist based on the selection from another dropdownlist in asp.net?

I have Dropdownlist1 which is bound to a database. Now based on the selected item in this dropdownlist, a list of items from the database should be displayed in Dropdownlist2.How to bind a list of items in a dropdownlist based on the selection from another dropdownlist in asp.net?
I assume you are binding that list to a SqlDataSource or something like that?





If this is the case what you can do is select ';Custom Query'; when creating your datasource, and within the control, you can then do something such as





';SELECT field1 from table2 where field2=@MYVAR';





What this does is allow you to then specify @MYVAR as a parameter, you are then prompted to choose what MYVAR is, select ';Control'; and the select DropDownList1's selected value.





You can then bind that to DropDownList2, once you have done that you can trigger a DataSource2.Databind() to refresh the data





EDIT : In case you didnt use the control, i thought I would update with the manual code:





Dim myConnection As OleDbConnection


Dim myCommand As OleDbCommand


Dim myReader As OleDbDatareader


Dim strSQL As String





myConnection = New OleDbConnection(';yourconnectionstring';)





strSQL=';SELECT field1,field2 from table2 where field2=''; %26amp; datalist1.selectedvalue.tostring %26amp; ';'';





myCommand = New OleDbCommand(strSQL, myConnection)





myConnection.Open()


myReader = myCommand.ExecuteReader()


While myReader.Read()


datalist2.Items.Add(new ListItem(myReader.GetString(1).ToString, myReader.GetString(0).ToString))


End While


myreader.close()


myConnection.Close()





Obviously those apostrophes ';''; and .GetStrings may vary depending on your record types :)How to bind a list of items in a dropdownlist based on the selection from another dropdownlist in asp.net?
In DropDownList1:


- Set the DataTextField and DataValueField properties of


- Set the AutoPostBack property of DropDownList1 to true.





- Handle the OnSelectedIndexChanged in your code behind to read the SelectedValue of the Item selected of DropDownList1 and use this SelectedValue to retrieve the DataSource of DropDownList2.





Hope this helps.