I have a datagridview with one of its column as TextBox. I wrote a function to populate values from database and suggest values to autocomplete the text. I achieved it, and then I started coding to make a column auto increment (Sr.No) , so I wrote some more lines of code and changed some properties and all of a sudden the textbox stopped auto-completing. Now I tried every possible step to make it work but failed. I dont know what is the property that I changed affected this. I am putting my code here, please help

This is the code for Editingcontrolshowing event...

Private Sub DataGridView2_EditingControlShowing(ByVal sender As System.Object, ByVal e As System.Windows.Forms.DataGridViewEditingControlShowingEventArgs) Handles DataGridView2.EditingControlShowing

    DataGridView2.BeginEdit(True)
    Dim autoText As TextBox = TryCast(e.Control, TextBox)
    If autoText IsNot Nothing Then
        autoText.AutoCompleteMode = AutoCompleteMode.SuggestAppend
        autoText.AutoCompleteCustomSource = AutoCompleteLoad()
        autoText.AutoCompleteSource = AutoCompleteSource.CustomSource
    End If
End Sub

This is the autocomplete function where I loaded values...

Public Function AutoCompleteLoad() As AutoCompleteStringCollection
    Dim str As AutoCompleteStringCollection = New AutoCompleteStringCollection()
    Dim ConnectionString As SqlConnection = New SqlConnection("data source=ADMIN-PC\SQLEXPRESS; database=billdev;Trusted_Connection=yes;")
    Dim strSQL As String = "SELECT * from bill;"
    Dim SQLcommand As New SqlCommand(strSQL, ConnectionString)
    ConnectionString.Open()
    Dim reader As SqlDataReader
    reader = SQLcommand.ExecuteReader()

    While reader.Read()
        str.Add(reader.Item(1))
    End While

    Return str

End Function

This is the extra code I added before it stopped working, but I think this doesn't make any difference

Private Sub DataGridView2_RowPrePaint(ByVal sender As System.Object, ByVal e As System.Windows.Forms.DataGridViewRowPrePaintEventArgs) Handles DataGridView2.RowPrePaint

    If e.RowIndex >= 0 Then
        Me.DataGridView2.Rows(e.RowIndex).Cells(0).Value = e.RowIndex + 1
    End If
End Sub