SELECT Unique rows from Datagridview using LINQ

问题

I am trying to SELECT ALL rows\columns from a datagridview where the first column is unique using LINQ.

Datagridview:

1     Blue     1111
1     Blue     1111
2     Green    1234
3     Orange   3211
2     Green    1234
4     Red      2222

Trying to get this Output:

1     Blue     1111
2     Green    1234
3     Orange   3211
4     Red      2222

I was able to use the following code which pulls all unique records from the first column but I am not sure how to get the remaining columns:

        Dim unique() As String = (From row As DataGridViewRow In dgvMaestro.Rows.Cast(Of DataGridViewRow)() _
         Where Not row.IsNewRow _
         Select CStr(row.Cells(0).Value)).Distinct.ToArray

        For Each a As String In unique
            Debug.Print(a)
        Next

Output:

Thanks

回答1:

First you need import 2 namespaces for distinct with linq to use AsEnumerable() method in DataTables and Field() method in DataRows

Imports System.Data.DataTableExtensions
Imports System.Data.DataRowExtensions

Declare new datatable

Dim NewTbl As New System.Data.DataTable

Add columns in you scenario

NewTbl.Columns.Add("ID", GetType(Integer))
NewTbl.Columns.Add("Color", GetType(String))
NewTbl.Columns.Add("Value", GetType(Integer))

Linq use Table 'TblValues' as you datasource

Dim results = (From row in TblValues.AsEnumerable() select col1 = row(Of Integer)("ID"), col2 = row(Of String)("Color"), col3 = row(Of Integer)("Value")).Distinct().ToList()

Iterate elements in results with for each, the reason is because results is an object datarow collection and isn't convert auto to table

For each r in results
  Dim Row as System.Data.DataRow = NewTbl.NewRow
  Row("ID") = r.col1
  Row("Color") = r.col2
  Row("Value") = r.col3
  NewTbl.Rows.Add(Row)
next

Now you have a DataTable 'NewTbl' with distinct values inside

回答2:

The best way to solve this is to write a comparer to compare the entire row.

Dim noduplicates = dgvMaestro.Rows.Cast(Of DataGridViewRow).Distinct(New RowComparer())

There are some examples of comparers on msdn

来源：https://stackoverflow.com/questions/20058026/select-unique-rows-from-datagridview-using-linq

标签

vb.net

linq

datagridview

distinct