Question

I have a textbox in a formview that gets its data from a linqdatasource which is used to enter a date:

<SP:TextBox ID = "StartDate" 
            Type = "Date" 
            Runat = "server" 
            Text = '<%# Bind("StartDate", "{0:yyyy-MM-dd}") %>' />

It works fine, except when StartDate is a null value in the database. Then the StartDate textbox is empty which is correct, but when the empty field is saved back to the database the date 0001-01-01 is stored instead of a null value which is wrong. How can I detect this scenario and turn the empty string into a null value before it is saved?

Answer 1

The solution is to add parameters for the nullable columns and set ConvertEmptyStringToNull to true:

<asp:LinqDataSource ID="LinqDataSource1" runat="server"
    ContextTypeName="NullUpdateRepo.DatabaseLinqDataContext" EnableUpdate="True"
    TableName="SampleTables" OnSelected="OnSelected" OnContextCreated="OnContextCreated">
    <UpdateParameters>
        <asp:Parameter Name="firstname" Type="String" ConvertEmptyStringToNull="true" />
        <asp:Parameter Name="lastname" Type="String" ConvertEmptyStringToNull="true" />
    </UpdateParameters>
</asp:LinqDataSource> 

http://connect.microsoft.com/VisualStudio/feedback/details/296161/linqdatasource-and-null-column-values