代码如下：
'去除重复，DtSource为datatable数据，记录40余万条
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
Dim dVidw As New DataView(DtSource)
Dim columnname(DtSource.Columns.Count - 1) As String
For i As Integer = 0 To DtSource.Columns.Count - 1
columnname(i) = DtSource.Columns(i).ColumnName
Next
Dim tempdt As New DataTable
tempdt = dVidw.ToTable(True, columnname) ‘这句执行的时间极长
DataGridView1.DataSource = tempdt
End Sub
我要把DtSource中重复的记录排除，以上代码一个小时还未执行完成，如何解决？
不要说提取数据时在SQL语句中使用去重功能，因为DtSource是由多个数据表合并而成的。
------解决方案--------------------
就是跨数据库的多个表都可以连在一起查询，为什么不在sql中处理？
------解决方案--------------------
试试这个。
Public Shared Function SelectDistinct(ByVal SourceTable As DataTable, ByVal ParamArray FieldNames() As String) As DataTable
Dim lastValues() As Object
Dim newTable As DataTable
If FieldNames Is Nothing OrElse FieldNames.Length = 0 Then
Throw New ArgumentNullException("FieldNames ")
End If
lastValues = New Object(FieldNames.Length - 1) {}
newTable = New DataTable
For Each field As String In FieldNames
newTable.Columns.Add(field, SourceTable.Columns(field).DataType)
Next
For Each Row As DataRow In SourceTable.Select(" ", String.Join(", ", FieldNames))
If Not fieldValuesAreEqual(lastValues, Row, FieldNames) Then
newTable.Rows.Add(createRowClone(Row, newTable.NewRow(), FieldNames))
setLastValues(lastValues, Row, FieldNames)
End If
Next
Return newTable
End Function
Private Shared Function fieldValuesAreEqual(ByVal lastValues() As Object, ByVal currentRow As DataRow, ByVal fieldNames() As String) As Boolean
Dim areEqual As Boolean = True
For i As Integer = 0 To fieldNames.Length - 1
If lastValues(i) Is Nothing OrElse Not lastValues(i).Equals(currentRow(fieldNames(i))) Then
areEqual = False
Exit For
End If
Next
Return areEqual
End Function
Private Shared Function createRowClone(ByVal sourceRow As DataRow, ByVal newRow As DataRow, ByVal fieldNames() As String) As DataRow
For Each field As String In fieldNames
newRow(field) = sourceRow(field)
Next
Return newRow
End Function
Private Shared Sub setLastValues(ByVal lastValues() As Object, ByVal sourceRow As DataRow, ByVal fieldNames() As String)
For i As Integer = 0 To fieldNames.Length - 1