StrataFrame Forum » StrataFrame Application Framework - V1 » Business Objects and Data Access (How do I?) » Dynamic conversion based on business object field data type

Dynamic conversion based on business object field data type

Tim Dol — Thu, 22 Oct 2009 08:40:24 GMT

I am trying to write a generic import routine that imports data into a business object and need some help on data conversion issue.

Example:

Say I have a datatable containing the data I want to import. Assume the column names in the import file match the business object's column names.

I have my customer object and want to populate it.

Dim loBO as New CustomerBO

For Each Row As DataRow In ImportFileDataTable.Rows

loBO.NewRow()
loBO.CurrentRow.Item("CompanyName") = Row.Item("CompanyName")

etc...

Next

This works fine but now I want to ensure the data from the import file converts to the appropriate type based on the business object. Example: The BO field may be integer but the data coming from the import datatable may be string... I want to convert this to the proper type.

I tried this...

Dim loType as Type
Dim loBO as New CustomerBO

For Each Row As DataRow In ImportFileDataTable.Rows

loBO.NewRow()

loType = GetType(loBO.CurrentRow.Item("CompanyName").GetType
loBO.CurrentRow.Item("CompanyName") = Ctype(Row.Item("CompanyName"),loType)

etc...

Next

Problem is 'loType' is not a valid variable for this statement... Is there anyway to dynamically set this type according to the data type on the business object without have to add a bunch of conditional statements?

Thanks,
Tim

RE: Dynamic conversion based on business object field data type

Ivan George Borges — Thu, 22 Oct 2009 08:40:24 GMT

Hi Tim!

I will throw some ideas of what I have done here to get "types". Maybe it can help you.

To get a System.Type of a SqlDBType:

[codesnippet]

    ''' <summary>
    ''' Find out the SqlDbType of a System.Type variable
    ''' </summary>
    ''' <param name="theType"></param>
    ''' <returns></returns>
    ''' <remarks></remarks>
    Public Shared Function GetDBType(ByVal theType As System.Type) As SqlDbType
        Dim p1 As SqlClient.SqlParameter
        Dim tc As System.ComponentModel.TypeConverter
        p1 = New SqlClient.SqlParameter()
        tc = System.ComponentModel.TypeDescriptor.GetConverter(p1.DbType)
        If tc.CanConvertFrom(theType) Then
            p1.DbType = CType(tc.ConvertFrom(theType.Name), DbType)
        Else
            'Try brute force
            Try
                p1.DbType = CType(tc.ConvertFrom(theType.Name), DbType)
            Catch ex As Exception
                'Do Nothing
            End Try
        End If
        Return p1.SqlDbType
    End Function
[/codesnippet]

To find out a Column type, in order to set defaults:

[codesnippet]

        '-- set default value
        Dim lb As Byte
        lb = CType(0, Byte)
        Select Case columnType.ToString
            Case "System.String"
                col.DefaultValue = ""
            Case "System.Int32"
                col.DefaultValue = CType(0, Integer)
            Case "System.Boolean"
                col.DefaultValue = False
            Case "System.Decimal"
                col.DefaultValue = CType(0, Decimal)
            Case "System.Byte"
                col.DefaultValue = CType(0, Byte)
            Case "System.DateTime"
                col.DefaultValue = "1800-01-01 00:00:00.000"
        End Select
[/codesnippet]

To convert a System.Data.DbType into a System.Type:

[codesnippet]

    Public Shared Function GetSystemType(ByVal DbType As System.Data.DbType) As System.Type
        '-- establish locals
        Dim stType As System.Type = GetType(System.String)
        '-- test the sent DbType
        Select Case DbType
            Case Data.DbType.String, Data.DbType.AnsiString, Data.DbType.AnsiStringFixedLength, _
             Data.DbType.StringFixedLength
                stType = GetType(System.String)
            Case Data.DbType.Int32
                stType = GetType(System.Int32)
            Case Data.DbType.Boolean
                stType = GetType(System.Boolean)
            Case Data.DbType.Decimal, Data.DbType.Currency
                stType = GetType(System.Decimal)
            Case Data.DbType.Byte, Data.DbType.SByte
                stType = GetType(System.Byte)
            Case Data.DbType.Date, Data.DbType.DateTime, Data.DbType.DateTime2
                stType = GetType(System.DateTime)
        End Select
        '-- return converted System.Type
        Return stType
    End Function

[/codesnippet]

RE: Dynamic conversion based on business object field data type

Tim Dol — Wed, 21 Oct 2009 20:33:42 GMT

I tried that Peter. Visual Studio displays a syntax error 'Type loBO.CurrentRow.Item is not defined'

RE: Dynamic conversion based on business object field data type

Peter Jones — Wed, 21 Oct 2009 18:31:11 GMT

Hi Tim,

This is out of my league but couldn't you use:

loBO.CurrentRow.Item("CompanyName") = Ctype(Row.Item("CompanyName"), GetType(loBO.CurrentRow.Item("CompanyName").GetType)

But this code will, of course, fail if the data can't be conversted , e.g. "ABC" into an integer.

Cheers, Peter