Is there a way to select columns in an linq statement based on if they exists in the datatable?

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I am trying to create a linq query that will fit priority sorting. However, not all tables have the same columns.

  Public Function Custom_sort(dt As DataTable) As DataView

      Custom_sort = dt.AsEnumerable().
        OrderBy(Function(row) String.IsNullOrWhiteSpace(row.Field(Of String)("Employee_SSN"))).

if dt.columns.exists("Group_number") then
ThenBy(Function(row) String.IsNullOrWhiteSpace(row.Field(Of String)("Group_number"))).
end if

AsDataView.totable

return custom_sort

end function

What I have tried:

I have tried the above-written statement and I have tried an encapsulated if() statement, but neither worked.

Posted 27-Nov-22 5:00am

Member 11856456

Updated 27-Nov-22 23:37pm

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[no name] 27-Nov-22 12:04pm

You want a "generic entity class" for different tables. LINQ deals with entities. How you fill those entities and from which tables, is up to you. It would (probably) only work in a query capacity unless you want to dig a realy deep hole. Think again why you think you need a "generic entity" (e.g. false economy).

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Richard Deeming · Answer 1 · 2022-11-27T23:37:00

You need to build up the query in a local variable:

VB.NET

Public Function Custom_sort(ByVal dt As DataTable) As DataView
    Dim rows As OrderedEnumerableRowCollection = dt.AsEnumerable().
        OrderBy(Function(row) String.IsNullOrWhiteSpace(row.Field(Of String)("Employee_SSN")))
    
    If dt.Columns.Contains("Group_number") Then
        rows = rows.ThenBy(Function(row) String.IsNullOrWhiteSpace(row.Field(Of String)("Group_number")))
    End If
    
    Return rows.AsDataView()
End Function