Vb.net | how to summary gridviewdata to another gridviewdata

Using Linq[^]...

Assuming that your DataGridView1 control is bind with DataTable object, you can create another datatable object and fill-in it with grouped data. For example:

'for test purposes only
'Dim dt As DataTable = New DataTable()
'dt.Columns.Add(New DataColumn("Name", Type.GetType("System.String")))
'dt.Columns.Add(New DataColumn("Hours", Type.GetType("System.Int32")))
'dt.Rows.Add(New Object(){"Name1", 1})
'dt.Rows.Add(New Object(){"Name1", 1})
'dt.Rows.Add(New Object(){"Name1", 2})
'dt.Rows.Add(New Object(){"Name1", 3})
'dt.Rows.Add(New Object(){"Name1", 1})
'dt.Rows.Add(New Object(){"Name2", 3})
'dt.Rows.Add(New Object(){"Name2", 3})
'dt.Rows.Add(New Object(){"Name2", 3})

'get datatable object
Dim dt As DataTable = DirectCast(DataGridView1.DataSource, DataTable)
'create a datasource for DataGridView2
Dim dt2 As DataTable = dt.Clone()
'fill-in a datatable object
dt2 = dt.AsEnumerable() _
	.GroupBy(Function(x) x.Field(Of String)("Name")) _
	.Select(Function(grp) dt2.LoadDataRow( New Object(){ _
			grp.Key, _
			grp.Sum(Function(x) x.Field(Of Integer)("Hours")) _
		}, False)) _
	.CopyToDataTable()
'bind data
DataGridView2.DataSource = dt2

In case, you've got unbounded DataGridView control, you can operate on DataGridView's rows:

Dim result = dgv.Rows.Cast(Of DataGridViewRow)() _
	.GroupBy(Function(x) x.Cells(0).Value) _
	.Select(Function(grp) New With _
		{
			.Name = grp.Key, _
			.Hours = grp.Sum(Function(x) x.Cells(1).Value) _
		}) _
	.ToList()
DataGridView2.DataSource = result