Ken Tucker

Here is a quick example on using an autocomplete combobox in the DataGridView.  In this example I load all the possible values for the combobox into a AutoCompleteStringCollection and make that the DataGridViewComboBox's datasource.  In the editingControl showing event you need to set the ComboBox's DropDownStyle, and the auto complete settings.

Imports System.Data.SqlClient

Public Class Form1
    Dim scAutoComplete As New AutoCompleteStringCollection

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim strConn As String
        Dim da As SqlDataAdapter
        Dim conn As SqlConnection
        Dim ds As New DataSet
        strConn = "Server = .\SQLEXPRESS;Database = NorthWind; Integrated Security = SSPI;"
        conn = New SqlConnection(strConn)
        da = New SqlDataAdapter("Select * from [Orders]", conn)
        da.Fill(ds, "Orders")
        DataGridView1.DataSource = ds.Tables("Orders")

        Dim cmd As New SqlCommand("Select CustomerID From customers", conn)
        Dim dr As SqlDataReader
        conn.Open()
        dr = cmd.ExecuteReader
        Do While dr.Read
            scAutoComplete.Add(dr.GetString(0))
        Loop
        conn.Close()

        Dim dgvcbc As New DataGridViewComboBoxColumn
        With dgvcbc
            .DataPropertyName = "CustomerID"
            .DataSource = scAutoComplete
            .HeaderText = "Customer ID"
        End With
        DataGridView1.Columns.Remove("CustomerID")
        DataGridView1.Columns.Insert(1, dgvcbc)
    End Sub

    Private Sub DataGridView1_EditingControlShowing(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewEditingControlShowingEventArgs) Handles DataGridView1.EditingControlShowing
        If DataGridView1.CurrentCell.ColumnIndex = 1 AndAlso TypeOf e.Control Is ComboBox Then
            With DirectCast(e.Control, ComboBox)
                .DropDownStyle = ComboBoxStyle.DropDown
                .AutoCompleteMode = AutoCompleteMode.SuggestAppend
                .AutoCompleteSource = AutoCompleteSource.CustomSource
                .AutoCompleteCustomSource = scAutoComplete
            End With
        End If
    End Sub

End Class