When exactly is a value returned from Eval() converted to a string?

Question

Hi

I thought Eval("JobTitle") converts returned value to type String, but that doesn’t seem to be the case, since value (returned by Eval("JobTitle")) passed to GetSelectedJobTitle() was of type Object and not String, which caused an error saying “cannot convert from object to string”.

<EditItemTemplate>
    <asp:DropDownList ID="EditJob" runat="server" 
           SelectedIndex='<%# GetSelectedJobTitle(Eval("JobTitle")) %>'
           DataSource=’<%# Titles %>’>    
    </asp:DropDownList>
</EditItemTemplate>


public int GetSelectedJobTitle(string title)
{
    ...
}

public string[] Titles
{
    ...
}

a) So when does the conversion (from Object to String) of value returned from Eval("JobTitle")) happen then?

b) And if Eval doesn’t do the conversion, what method does?

thanx

EDIT:

I assume that in our example GetSelectedJobTitle() is called before Asp.Net evaluates ( and converts it to string ) the expression contained inside <%# %>?

Answer 1

Eval returns "object". You have to cast it to a string if you know that you'll get a string.

<EditItemTemplate>
    <asp:DropDownList ID="EditJob" runat="server" 
           SelectedIndex='<%# GetSelectedJobTitle((string)Eval("JobTitle")) %>'
           DataSource=’<%# Titles %>’>    
    </asp:DropDownList>
</EditItemTemplate>

The conversion happens during the DataBind Event.

EDIT: Better answer the comments here.

Our big difference is that statement:

Yours:

<%# GetSelectedJobTitle(Eval("JobTitle")) %>

gives me also a

Error 2 Argument '1': cannot convert from 'object' to 'string' p:\WebSite1\Default.aspx 19

Mine:

<%# GetSelectedJobTitle((string)Eval("JobTitle")) %>

Compiles!