如何比较重复vb.net的2个datagridview列

Question

我很难搞清楚这一点。我有2个DataGridViews，我需要比较每个列的1列并突出显示重复项。我从SQL数据库填充DataGrids。我到目前为止的代码如下。所有这一切都突出了每一行。我不确定如何让它查看列并找到任何重复的值，而不只是在同一行号。

        Dim RowOut As Integer
    Dim RowIn As Integer
    For Each rowOuter As DataGridViewRow In listOrderGrid.Rows
        For Each rowInner As DataGridViewRow In listWebPollingGrid.Rows
            RowOut = rowOuter.Cells("OrderID").Value
            RowIn = rowInner.Cells("OrderID").Value
            If rowInner.Cells("OrderID").Value = rowOuter.Cells("OrderID").Value Then
                rowOuter.DefaultCellStyle.BackColor = Color.LightGreen
                rowInner.DefaultCellStyle.BackColor = Color.LightGreen
            End If
            If rowOuter.Cells("OrderTypeName").Value = "Paid Out" Then
                rowOuter.DefaultCellStyle.BackColor = Color.Violet
            End If
        Next
    Next