How to store the class result in the variable created the class?

Question

Hi

Well, I was just wondering about this 

If I code

Dim mydt As New Datatable

......

Later on, I can code 

Mydatagridview.Datasource = mydt

If you note, I used the variable mydt which create the class Datatable without using any property/sub/function

If I create my own class

Public Class mydatatable
    Property my_prop_dt As DataTable
End Class

the only way (As I know) to use it like that

Dim oMyClass As New mydatatable
mydatagridview.datasource = oMyClass.my_prop_dt

The same if I used function instead of property

What I want or looking to see if that is applicable is :

Dim oMyClass As New mydatatable
mydatagridview.datasource = oMyClass

Can I use the variable oMyclass to store the result I want same behaviour as Dim oMyClass as New Datatable ?

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Answer 1

Hi,

Yes .. you have tyo inherit it from datatable

Regards,

Stygen

Answer 2

@Stygen

I thought about that, but... 

Public Class MyDatatable
    Inherits DataTable
    Sub new
        MyDatatable = New DataTable() ' <-- error Mydatatable is type and cannot be used as an expression
    End Sub
End Class

I got error in bolded line

How/Where to store the result to the class itself?

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Answer 3

I got error in bolded line

How/Where to store the result to the class itself?

There is no need for the sub New.    Creating your class and inheriting from the type DataTable means that your class instance can be used just like a DataTable object.   Why do you want to use your own class?

Option Strict On
Public Class Form1

    Private Sub Form1_Load(ByVal sender As Object, ByVal e As EventArgs) Handles MyBase.Load
        Dim oMyClass As New MyDatatable
        mydatagridview.datasource = oMyClass
End Class

Public Class MyDatatable
    Inherits DataTable
End Class

Answer 4

   Why do you want to use your own class?

Hi Acamar

I want to create or add my own custum properties/sub/function to myclass which is based on Datatable such as

Partial Class MyDatatable
    Inherits DataTable
    Function ExecuteToDatatable(TableName As String,Query As String)
        Dim dt As New DataTable(TableName)
        '.... some code to fille the dt
        ' Save the result of dt to Class <---
    End Function
End Class

so Later I can code 

mydatagridview.datasource = oMyClass

This is a thought I was thinking in to see if its doable, that is all.

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Answer 5

I want to create or add my own custum properties/sub/function to myclass which is based on Datatable 

You can do that - that's what Inherits is all about.   Once you have created your custom class that inherits from a datatable you can add methods and functions to enhance it.  For instance, you might create a method that initialises it (the Clear method) and then loads some data into it (using Load) and so on.   For your example code above you would provide a method that returns a new datatable

Public Class MyDatatable
    Inherits DataTable
    Function ExecuteToDatatable(TableName As String,Query As String) as MyDataTable
        Dim dt As New MyDataTable(TableName)
        '.... some code to fill the dt
        Return dt
    End Function
End Class

so your application code is

        Dim oMyClass As New MyDatatable
        ...
        oMyClass = oMyClass.ExecuteToDatatable(SourceTable, QueryString)

Answer 6

@Acamar : Nice Trick :)

I was testting code and that works of how I want it.

Thanks for your effort.

Dim o As New MyDatatable
Me.DataGridView5.DataSource = o

Public Partial Class MyDatatable

    Inherits datatable
    Sub New
        MyBase.Columns.Add("A",GetType(Integer))
        MyBase.Columns.Add("B",GetType(String))
        MyBase.Rows.Add({1,"one"})
    End Sub
End Class

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Answer 7

The real answer to my question was using MyBase.Rows.Add()

Which I found while I was trying.

Thanks every one.

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