ASP .NET, LINQ, GridViews, and GUID Errors

I found a simple problem today. Here is the deal, there were several times where I had to base a LinqDataSource off a Guid that I would set in the Page_Load(). I created an<asp:HiddenField /> to hold the value so all my DataSources could pull it from the control. The HiddenField control’s value is stored as a string, so I would have to convert the guid to a string. After doing this, I was getting the following error:

Operator ‘==’ incompatible with operand types ‘Guid’ and ‘String’

After looking around in my code and some forums, I found the answer: Linq is strongly cast and Visual Studio 2008 most like set the “where” clause to something like this:

<asp:LinqDataSource ID=”ldsProducs” runat=”server”

        ContextTypeName=”CartDataContext” EnableDelete=”True” EnableInsert=”True”

        EnableUpdate=”True” OrderBy=”Product_UPC1″ TableName=”Product_UPCs”

        Where=”Product_IID == @Product_IID”>

        <WhereParameters>

            <asp:ControlParameter ControlID=”hfProductIID” Name=”Product_IID”

                PropertyName=”Value” Type=”Object” />

        </WhereParameters>

    </asp:LinqDataSource>

 However, because Linq is strongly cast you can’t perform an == operand on a String and Guid, so I changed the following:

<asp:LinqDataSource ID=”ldsProducs” runat=”server”

        ContextTypeName=”CartDataContext” EnableDelete=”True” EnableInsert=”True”

        EnableUpdate=”True” OrderBy=”Product_UPC1″ TableName=”Product_UPCs”

        Where=”Product_IID == Guid(@Product_IID)”>

        <WhereParameters>

            <asp:ControlParameter ControlID=”hfProductIID” Name=”Product_IID”

                PropertyName=”Value” Type=”Object” />

        </WhereParameters>

    </asp:LinqDataSource>

 Now it’ll convert the HiddenField’s value to a Guid and compair.

Related Posts

1. ASP .NET, GridViews, SqlDataSource, and Guid Parameters Another thing I ran into today. I actually ran into it awhile back but since I ran into it again today I’d thought I’d post on it to help anyone who happens to find it. Problem You have a GridView and a SqlDataSource that takes 1 or more Guids as...
2. ASP .NET 2.0, GridViews, HyperLinkField, and JavaScript I’ve found some interesting notes on ASP .NET’s GridView, it’s limitations and work arounds. For work I was looking for a way to execute JavaScript from clicking a link on a GridView Cell. An example would be to having a list of transactions and wanting to click a link to...
3. LINQ and NOT IN Queries Found an excellent blog post on how to do NOT IN scenarios using .Contains()....