Need Generic Utility Method C# for Populating Asp.net DropDownList

Question

I have a method like the following in a Utility class. I would like to change the parameter dataSource to accept any type of datasource i.e. dataset, dataview, List, datatable, arraylist.

Is this possible? How would I change the method signature (and parameters and types) to allow me the flexibility of passing in any acceptable datasource for binding?

Thank you

public void FillCombo(DropDownList ddl, DataTable dataSource, string textField, string valueField, bool addSelect) {

    ddl.DataValueField = valueField;
    ddl.DataTextField = textField;
    ddl.DataSource = dataSource;
    ddl.DataBind();

    if (addSelect) AddSelectCombo(ddl, "Select", -1);

}

Answer 1

I believe the following is what you're looking for.

public void FillCombo<TSource>(DropDownList ddl, TSource dataSource, string textField, string valueField, bool addSelect) {

    ddl.DataValueField = valueField;
    ddl.DataTextField = textField;
    ddl.DataSource = dataSource;
    ddl.DataBind();

    if (addSelect) AddSelectCombo(ddl, "Select", -1);

}

Answer 2

Well, since the DataSource property on a DropDownList has type object you could change your method signature to accept an object. That would not make your method generic (in the .net sense), but maybe it would be enough anyway.

Answer 3

I have something similar in my library, and what I did is create it as an Extension method (.NET 3.5+) on the DropDownList class...

Imports WC = System.Web.Controls

...

<Extension()> Public Sub DataBindEx(
    ByVal target As WC.DropDownList, ByVal DataSource As Object, 
    ByVal DataTextField As String, ByVal DataValueField As String,
    Optional ByVal SetTooltips As Boolean = True
)
    With target
        .DataSource = DataSource
        .DataTextField = DataTextField
        .DataValueField = DataValueField
        .DataBind()
    End With

    If SetTooltips Then
        For Each li As ListItem In target.Items
            li.Attributes("title") = li.Text
        Next
    End If
End Sub

I'll leave it for you to translate to C#.