Solved

Custom CType Function That you define the "type" to convert to at runtime  -- Anyone have an any ideas

Posted on 2004-03-26
3
824 Views
Last Modified: 2010-05-18
I have wrtten a working solution that converts a datarow to a class, so I can manipulate it with the least pain, as I have to do this quite a bit I've written a base class to handle this for me that leverages reflection so it will work for any new classes I build. The code is below.

Public Sub FillClassFromDataSet(ByVal ds As DataSet, ByVal ClassToFill As Object, ByVal ClassType As Type)
        'This function converts the information in a dataset to a class
        'note for this method to be usable the properties of the class must match the
        'column names in the dataset
        Dim dc As System.Data.DataColumn
        Dim dr As System.Data.DataRow
        Try
            'Get the data row to convert
            dr = ds.Tables(0).Rows(0)
            'For each column in our data row attempt to convert the value to class value
            For Each dc In ds.Tables(0).Columns
                'arglist is the object we use to pass the value to our class property
                Dim arglist(0) As Object
                'Get the system type of the class proeprty we are trying to convert to
                Dim PropertyInfo As System.Reflection.PropertyInfo = ClassType.GetProperty(dc.ColumnName)
                'Check to make sure we have a corresponding property in the class to
                'match our column name
                If Not PropertyInfo Is Nothing Then
                    'based on the proprety type perform the appropriate conversion on the
                    'value we want to pass to the class property
                    Select Case PropertyInfo.PropertyType.ToString
                        Case "System.String" : arglist(0) = CType(dr(dc.Ordinal), System.String)
                        Case "System.Int16" : arglist(0) = CType(dr(dc.Ordinal), System.Int16)
                        Case "System.Int32" : arglist(0) = CType(dr(dc.Ordinal), System.Int32)
                        Case "System.Int64" : arglist(0) = CType(dr(dc.Ordinal), System.Int64)
                        Case "System.DateTime" : arglist(0) = CType(dr(dc.Ordinal), System.DateTime)
                        Case "System.Double" : arglist(0) = CType(dr(dc.Ordinal), System.Double)
                        Case "System.Decimal" : arglist(0) = CType(dr(dc.Ordinal), System.Decimal)
                        Case "System.Decimal" : arglist(0) = CType(dr(dc.Ordinal), System.Decimal)
                        Case Else
                            'An handled type    
                            Throw New System.Exception("Unhandled Property Type (" & PropertyInfo.PropertyType.ToString & ") in FillClassFormDataSet")
                    End Select
                    Try
                        'Now pass the value from the datacolumn to the correspoding class proprety
                        ClassType.InvokeMember(dc.ColumnName, Reflection.BindingFlags.SetProperty, Nothing, ClassToFill, arglist)
                    Catch ex As Exception
                        Dim x As String = ex.Message
                    End Try
                Else
                    Throw New System.Exception("Unknown Property (" & dc.ColumnName & ") in FillClassFormDataSet")
                End If
            Next
        Catch ex As Exception
            Console.WriteLine(ex.Message)
        End Try

    End Sub

This code is ok but it only handles conversions for the types that I have defined in the class, int32, string and so on.

The problem is this I'd like to replace the whole select statement that gets the type of the property and does the appropriate conversion with the following lines

Dim PropertyType As Type = PropertyInfo.PropertyType
CType(dr(dc.Ordinal), PropertyType)

This way I could handle any/all types that could be safely stored in a db and won't have to worry about constantly updating my class

Of course the Ctype function only excepts system defined types and won't except my variable pointing to the type I'd like it converted to :(

Anyone know a way to get around this behaviour, I checked out the basetype for Ctype but it looks like evetually I'm still going to have the same problem and be back to my original verbose solution. Any ideas, help would be appreciated





0
Comment
Question by:NotaClue
  • 2
3 Comments
 
LVL 6

Accepted Solution

by:
KarunSK earned 500 total points
Comment Utility
You can replace the Select Case construct with this line:

                    arglist(0) = Convert.ChangeType(dr(dc.Ordinal), PropertyInfo.PropertyType)

HTH,
Karun.
0
 
LVL 1

Author Comment

by:NotaClue
Comment Utility
Thanks Karen,

Exactly want I needed
0
 
LVL 6

Expert Comment

by:KarunSK
Comment Utility
Can you tell me why this question has been rated "B"?
0

Featured Post

How your wiki can always stay up-to-date

Quip doubles as a “living” wiki and a project management tool that evolves with your organization. As you finish projects in Quip, the work remains, easily accessible to all team members, new and old.
- Increase transparency
- Onboard new hires faster
- Access from mobile/offline

Join & Write a Comment

A long time ago (May 2011), I have written an article showing you how to create a DLL using Visual Studio 2005 to be hosted in SQL Server 2005. That was valid at that time and it is still valid if you are still using these versions. You can still re…
Real-time is more about the business, not the technology. In day-to-day life, to make real-time decisions like buying or investing, business needs the latest information(e.g. Gold Rate/Stock Rate). Unlike traditional days, you need not wait for a fe…
Access reports are powerful and flexible. Learn how to create a query and then a grouped report using the wizard. Modify the report design after the wizard is done to make it look better. There will be another video to explain how to put the final p…
This video explains how to create simple products associated to Magento configurable product and offers fast way of their generation with Store Manager for Magento tool.

728 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

10 Experts available now in Live!

Get 1:1 Help Now