working with datasets

I get a error (Object reference not set to an instance of an object.) in the attached code on this line:

dt.Columns.Add(New DataColumn("Path"))


Dim DS As New DataSet()
            Dim dt As DataTable = DS.Tables("Category")


            For i = 1 To col.Count
                cID = col.Item(i).ToString()

            

                dt.Columns.Add(New DataColumn("Path"))
                'dt.Columns.Add(New DataColumn("ParentName"))

                dt.Rows(0)("Path") = "/" & ReturnCategoryPath(cID)

            Next

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vbnetcoderAsked:
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Wayne Taylor (webtubbs)Commented:
Your DataTable doesn't yet exist because you have only just created a new DataSet (which has no DataTables to begin with).

I assume you want to add a DataTable "Category" to your DataSet? If so, then you first need to create that DataTable and add it to your DataSet....

        Dim DS As New DataSet()
        Dim dt As New DataTable("Category")
        DS.Tables.Add(dt)

        For i = 1 To col.Count
                cID = col.Item(i).ToString()            

                dt.Columns.Add("Path")
                dt.Columns.Add("ParentName")

                dt.Rows(0)("Path") = "/" & ReturnCategoryPath(cID)

        Next

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Wayne
0
vbnetcoderAuthor Commented:
Now, i get a error at

dt.Rows(0)("Path") = "/" & ReturnCategoryPath(cID)

The error is:

There is no row at position 0.
0
Wayne Taylor (webtubbs)Commented:
Ahh, yes, a newly created table also has no DataRows, so you'll have to create them and add them to the table...

        Dim DS As New DataSet()
        Dim dt As New DataTable("Category")
        DS.Tables.Add(dt)

        For i = 1 To col.Count
                cID = col.Item(i).ToString()            

                dt.Columns.Add("Path")
                dt.Columns.Add("ParentName")

                Dim dr As DataRow = dt.NewRow()
                dr("Path") = "/" & ReturnCategoryPath(cID)
                
                dt.Rows.Add(dr)

        Next

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0

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vbnetcoderAuthor Commented:
ty
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