SAMPLE:1
Dim qry0 = From theRow As DataGridViewRow In dgvData.Rows _
Select theRow
Dim t = qry0.Sum(Function(x As DataGridViewRow) x.Cells("Amount").Value)
** dgvData - Datagridview name "Anount" is column name
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SAMPLE:2
Dim qry1 = From theRow As DataGridViewRow In dgvData.Rows _
Where theRow.Cells("Year").Value > 2010 _
Select theRow
Dim t = qry1.Sum(Function(x As DataGridViewRow) x.Cells("Amount").Value)