Public Class SQLJoiner
    Public dtJoin As DataTable
    Public dtA As DataTable
    Public dtB As DataTable
    Public OuterJoin As Boolean = False

    Public Sub JoinSchema()
        Dim col As DataColumn
        Dim new_col As DataColumn
        Dim ds As New DataSet()

        dtJoin = dtA.Clone
        dtJoin.TableName = dtA.TableName & "_" & dtB.TableName
        ds.Tables.Add(dtJoin)
        For Each col In dtB.Columns
            If dtJoin.Columns.Contains(col.ColumnName) Then
                new_col = dtJoin.Columns.Add(col.ColumnName & Guid.NewGuid().ToString())
            Else
                new_col = dtJoin.Columns.Add(col.ColumnName)
            End If

            new_col.AllowDBNull = col.AllowDBNull
            new_col.DataType = col.DataType
            new_col.DefaultValue = col.DefaultValue
            new_col.MaxLength = col.MaxLength
            new_col.ReadOnly = col.ReadOnly
            new_col.Unique = col.Unique
        Next
    End Sub

    Public Sub JoinData(ByVal col_A As String, ByVal col_B As String)
        Dim ds As New DataSet()
        Dim full_row As ArrayList
        Dim rowA As DataRow
        Dim rowB As DataRow

        ds.Tables.Add(dtA)
        ds.Tables.Add(dtB)

        ds.Relations.Add("LOCAL_RELATION", dtA.Columns(col_A), dtB.Columns(col_B))
        For Each rowA In dtA.Rows
            If OuterJoin OrElse (rowA.GetChildRows("LOCAL_RELATION").Length >  0 ) Then
                Dim row_Added As Boolean = False
                For Each rowB In rowA.GetChildRows("LOCAL_RELATION")
                    full_row = New ArrayList(rowA.ItemArray)
                    full_row.AddRange(rowB.ItemArray)
                    dtJoin.LoadDataRow(full_row.ToArray(), True)
                    row_Added = True
                Next
                If Not row_Added AndAlso OuterJoin Then
                    Dim obj(dtB.Columns.Count -  1 ) As Object
                    full_row = New ArrayList(rowA.ItemArray)
                    full_row.AddRange(obj)
                    dtJoin.LoadDataRow(full_row.ToArray(), True)
                End If
            End If
        Next
    End Sub
End Class

Dim joiner As New SQLJoiner()
joiner.dtA = myDtA
joiner.dtB = myDtB
joiner.OuterJoin = True ' Если  OuterJoin = True то моделируем dtA LEFT OUTER JOIN dtB, 
joiner.JoinSchema() 'иначе dtA INNER JOIN dtB
joiner.JoinData(COLUMN_NAME_A, COLUMN_NAME_B)
result = joiner.dtJoin