Bind ASP.NET DropDownList DataTextField to method? - asp.net

Question

Is there anyway to have items in an ASP.NET DropDownList have either their Text or Value bound to a method on the source rather than a property?

Answer 1

This is my solution:
<asp:DropDownList ID="dropDownList" runat="server" DataSourceID="dataSource" DataValueField="DataValueField" DataTextField="DataTextField" />
<asp:ObjectDataSource ID="dataSource" runat="server" SelectMethod="SelectForDataSource" TypeName="CategoryDao" />
public IEnumerable<object> SelectForDataSource()
{
return _repository.Search().Select(x => new{
DataValueField = x.CategoryId,
DataTextField = x.ToString() // Here is the trick!
}).Cast<object>();
}

Answer 2

Here's 2 examples for binding a dropdown in ASP.net from a class
Your aspx page
<asp:DropDownList ID="DropDownListJour1" runat="server">
</asp:DropDownList>
<br />
<asp:DropDownList ID="DropDownListJour2" runat="server">
</asp:DropDownList>
Your aspx.cs page
protected void Page_Load(object sender, EventArgs e)
{
//Exemple with value different same as text (dropdown)
DropDownListJour1.DataSource = jour.ListSameValueText();
DropDownListJour1.DataBind();
//Exemple with value different of text (dropdown)
DropDownListJour2.DataSource = jour.ListDifferentValueText();
DropDownListJour2.DataValueField = "Key";
DropDownListJour2.DataTextField = "Value";
DropDownListJour2.DataBind();
}
Your jour.cs class (jour.cs)
public class jour
{
public static string[] ListSameValueText()
{
string[] myarray = {"a","b","c","d","e"} ;
return myarray;
}
public static Dictionary<int, string> ListDifferentValueText()
{
var joursem2 = new Dictionary<int, string>();
joursem2.Add(1, "Lundi");
joursem2.Add(2, "Mardi");
joursem2.Add(3, "Mercredi");
joursem2.Add(4, "Jeudi");
joursem2.Add(5, "Vendredi");
return joursem2;
}
}

Answer 3

The only way to do it is to handle the Databinding event of the DropDownList, call the method and set the values in the DropDownList item yourself.

Answer 4

Sometimes I need to use Navigation Properties as DataTextField, like ("User.Address.Description"), so I decided to create a simple control that derives from DropDownList.
I also implemented an ItemDataBound Event that can help as well.
public class RTIDropDownList : DropDownList
{
public delegate void ItemDataBoundDelegate( ListItem item, object dataRow );
[Description( "ItemDataBound Event" )]
public event ItemDataBoundDelegate ItemDataBound;
protected override void PerformDataBinding( IEnumerable dataSource )
{
if ( dataSource != null )
{
if ( !AppendDataBoundItems )
this.Items.Clear();
IEnumerator e = dataSource.GetEnumerator();
while ( e.MoveNext() )
{
object row = e.Current;
var item = new ListItem( DataBinder.Eval( row, DataTextField, DataTextFormatString ).ToString(), DataBinder.Eval( row, DataValueField ).ToString() );
this.Items.Add( item );
if ( ItemDataBound != null ) //
ItemDataBound( item, row );
}
}
}
}

Answer 5

Declaratively:
<asp:DropDownList ID="ddlType" runat="server" Width="250px" AppendDataBoundItems="true" DataSourceID="dsTypeList" DataTextField="Description" DataValueField="ID">
<asp:ListItem Value="0">All Categories</asp:ListItem>
</asp:DropDownList><br />
<asp:ObjectDataSource ID="dsTypeList" runat="server" DataObjectTypeName="MyType" SelectMethod="GetList" TypeName="MyTypeManager">
</asp:ObjectDataSource>
The above binds to a method that returns a generic list, but you could also bind to a method that returns a DataReader. You could also create your dataSource in code.