I have a varchar(max) field in SQL 2008 Dataset_XML. My strongly typed business object is mapped to that column, and returns

<dsPolicies xmlns="http://tempuri.org/dsPolicies.xsd" /> 

for a null. ( this is because I am adding this field to a current app an have to allow nulls, but I could script this as a value for all null values and then not allow nulls if that would help)

dsPolicies is dropped on the form and the instance is names dsPolicies1.

The dataset is typed with 8 tables. and the XSD file seems to be working as I am using bindingsources for each table and the datagridviews are showing the right columns.

In the parentform_loading event of the business object on the Policies form I am trying to deserialize the XML stored in Me.PoliciesBO1.Dataset_XML ( which has the default value shown above) using this code :

    Private Sub PoliciesBO1_ParentFormLoading() Handles PoliciesBO1.ParentFormLoading

        Me.PoliciesBO1.fillall()

        If Me.PoliciesBO1.Count > 0 Then

            Me.DsPolicies1 = _ CType(InsurtecPW.Base.Utility.SmartDeSerialize(Me.PoliciesBO1.Dataset_XML), InsurtecPW.dsPolicies)

        End If

    End Sub

and this is the deserialize routine :

    Public Shared Function SmartDeSerialize(ByVal serialized As String) As DataSet
        Dim __ds As DataSet = New DataSet
        ' needed to create an XML TextReader 
        Dim nt As NameTable = New NameTable
        Dim nsmgr As XmlNamespaceManager = New XmlNamespaceManager(nt)
        Dim context As XmlParserContext = New XmlParserContext(Nothing, nsmgr, Nothing, XmlSpace.None)
        Dim tr As XmlTextReader = New XmlTextReader(serialized, XmlNodeType.Document, context)
        Try

            __ds.ReadXml(tr)

            Return __ds
        Finally
            If Not (tr Is Nothing) Then
                tr.Close()
                tr = Nothing
            End If
            context = Nothing
            nsmgr = Nothing
            nt = Nothing

        End Try

    End Function

As you see, this returns a dataset, but I don't seem to be able to cast the return value as the dsPolicies that I need.

Unable to cast object of type 'System.Data.DataSet' to type 'InsurtecPW.dsPolicies'.

I have also tried a directcast of the returned dataset and got the same result.

This approach seemed to work find when I was using an untyped dataset.

I'd appreciate any thoughts on this. I'm pretty clueless about possible differences between the dataset class and a typed dataset or if my problem is the value I am returning if the column is empty.

I am open to any approach (including serializing to a byte array) which will allow me to write and entire dataset to a sql column and bring it back.

Suggestions very much appreciated.

TIA