Question

I have a ASP gridview control. I have a ASP label control in the item template column. I bind data to the grid using –

<ItemTemplate>
        <asp:Label ID="lblDesc" runat="server" Text='<%# Eval("Description") %>'></asp:Label>
</ItemTemplate>

But, the value of this string can be upto 80 characters. But, I cannot afford to have the column length to be so high. And, there are limitations so I cannot use Wrap="true" and limit the column width.

So, I figured the solution could be to display only about 50 characters in the grid and display the entire string as a tool tip. I managed to do this by using this –

<ItemTemplate>
        <asp:Label ID="lblDesc" runat="server" Text='<%# Eval("Description").ToString().Substring(0,50) %>' ToolTip='<%# Eval("Description") %>'></asp:Label>
</ItemTemplate>

This displays the first 50 characters of the string in the grid column. And, the complete string is displayed as a tool tip when the mouse pointer hovers over the text. But, the problem arises when the string length is less than 50 characters. In this case, an exception is thrown.

I tried modifying this piece of code to allow conditional display by checking for the string length. But, I could not get this to work.

Is there a way to fix this problem? Can we call a javascript function within Eval() ?

Answer 1

Whenever you need special handling for your databinding expressions, you can just make a helper function in your code-behind, such as

protected string EvalWithMaxLength(string fieldName, int maxLength)
{
    object value = this.Eval(fieldName);
    if (value == null)
        return null;
    string str = value.ToString();
    if (value.Length > maxLength)
        return value.SubString(0, maxLength);
    else
        return value;
}

In your ASPX/ASCX you can then say

<ItemTemplate>
    <asp:Label ID="lblDesc" runat="server" Text='<%# EvalWithMaxLength("Description", 50) %>' ToolTip='<%# Eval("Description") %>'></asp:Label>
</ItemTemplate>

If you’d like to separate the Eval and the truncate, you could make a general extension method like

public static class MyExtensions
{
    public static string ToStringTruncated(this object value, int maxLength)
    {
        if (value == null)
            return null;
        string str = value.ToString();
        if (value.Length > maxLength)
            return value.SubString(0, maxLength);
        else
            return value;
    }
}

and call

Text='<%# Eval("Description").ToStringTruncated(50) %>'

And because you’ve made this extension method for type object, you can now also say

1234.ToStringTruncated(3) // == "123"

Whether you’d like that is a matter of taste.