How to remove all duplicates in a data table in vb.net? - vb.net

Question

Consider my data table
ID Name
1 AAA
2 BBB
3 CCC
1 AAA
4 DDD
Final Output is
2 BBB
3 CCC
4 DDD
How can i remove the rows in the data table using Vb.Net
Any help is appreciated.

Answer 1

Following works if you only want the distinct rows(skip those with same ID and Name):
Dim distinctRows = From r In tbl
Group By Distinct = New With {Key .ID = CInt(r("ID")), Key .Name = CStr(r("Name"))} Into Group
Where Group.Count = 1
Select Distinct
' Create a new DataTable containing only the unique rows '
Dim tblDistinct = (From r In tbl
Join distinctRow In tblDistinct
On distinctRow.ID Equals CInt(r("ID")) _
And distinctRow.Name Equals CStr(r("Name"))
Select r).CopyToDataTable
If you want to remove the dups from the original table:
Dim tblDups = From r In tbl
Group By Dups = New With {Key .ID = CInt(r("ID")), Key .Name = CStr(r("Name"))} Into Group
Where Group.Count > 1
Select Dups
Dim dupRowList = (From r In tbl
Join dupRow In tblDups
On dupRow.ID Equals CInt(r("ID")) _
And dupRow.Name Equals CStr(r("Name"))
Select r).ToList()
For Each dup In dupRowList
tbl.Rows.Remove(dup)
Next
Here is your sample-data:
Dim tbl As New DataTable
tbl.Columns.Add(New DataColumn("ID", GetType(Int32)))
tbl.Columns.Add(New DataColumn("Name", GetType(String)))
Dim row = tbl.NewRow
row("ID") = 1
row("Name") = "AAA"
tbl.Rows.Add(row)
row = tbl.NewRow
row("ID") = 2
row("Name") = "BBB"
tbl.Rows.Add(row)
row = tbl.NewRow
row("ID") = 3
row("Name") = "CCC"
tbl.Rows.Add(row)
row = tbl.NewRow
row("ID") = 1
row("Name") = "AAA"
tbl.Rows.Add(row)
row = tbl.NewRow
row("ID") = 4
row("Name") = "DDD"
tbl.Rows.Add(row)

Answer 2

You can use the DefaultView.ToTable method of a DataTable to do the filtering like this:
Public Sub RemoveDuplicateRows(ByRef rDataTable As DataTable)
Dim pNewDataTable As DataTable
Dim pCurrentRowCopy As DataRow
Dim pColumnList As New List(Of String)
Dim pColumn As DataColumn
'Build column list
For Each pColumn In rDataTable.Columns
pColumnList.Add(pColumn.ColumnName)
Next
'Filter by all columns
pNewDataTable = rDataTable.DefaultView.ToTable(True, pColumnList.ToArray)
rDataTable = rDataTable.Clone
'Import rows into original table structure
For Each pCurrentRowCopy In pNewDataTable.Rows
rDataTable.ImportRow(pCurrentRowCopy)
Next
End Sub

Answer 3

Assuming you want to check all the columns, this should remove the duplicates from the DataTable (DT):
DT = DT.DefaultView.ToTable(True, Array.ConvertAll((From v In DT.Columns Select v.ColumnName).ToArray(), Function(x) x.ToString()))
Unless I overlooked it, this doesn't seem to be in the documentation (DataView.ToTable Method), but this also appears to do the same thing:
DT = DT.DefaultView.ToTable(True)