How to filter datagridview from 3 textboxes?

Question

hey, would you help me 
so, i have a form and connects to mdb database.
this is my code
Imports System.IO
Imports System.Data.OleDb
Public Class Form1
Private DBPath As String
Private conn As OleDbConnection
Private adapter As OleDbDataAdapter
Private dtMain As DataTable
Public Sub New()
InitializeComponent()
End Sub
Private Sub Form1_Load(ByVal sender As Object, ByVal e As EventArgs) Handles MyBase.Load
DBPath = Application.StartupPath + "\db.mdb"
If Not File.Exists(DBPath) Then
Dim cat As New ADOX.Catalog()
cat.Create(Convert.ToString("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=") & DBPath)
cat = Nothing
End If
conn = New OleDbConnection(Convert.ToString("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=") & DBPath)
conn.Open()
Try
Using cmd As New OleDbCommand("CREATE TABLE [Table_1] ([id] COUNTER PRIMARY KEY, [text_column] MEMO, [int_column] INT);", conn)
cmd.ExecuteNonQuery()
End Using
Catch ex As Exception
If ex IsNot Nothing Then
ex = Nothing
End If
End Try
Using dt As DataTable = conn.GetSchema("Tables")
For i As Integer = 0 To dt.Rows.Count - 1
If dt.Rows(i).ItemArray(dt.Columns.IndexOf("TABLE_TYPE")).ToString() = "TABLE" Then
ComboBoxTables.Items.Add(dt.Rows(i).ItemArray(dt.Columns.IndexOf("TABLE_NAME")).ToString())
End If
Next
End Using
End Sub
Private Sub button1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button1.Click
If ComboBoxTables.SelectedItem Is Nothing Then
Return
End If
adapter = New OleDbDataAdapter("SELECT * FROM [" + ComboBoxTables.SelectedItem.ToString() + "]", conn)
Dim builder = New OleDbCommandBuilder(adapter)
dtMain = New DataTable()
adapter.Fill(dtMain)
DataGridView1.DataSource = dtMain
End Sub
End Class
and now i have 4 textbox and 4 column table of database.
for example, this is my table :
and if i type :
textbox 1 : "1"
textbox 2 : "2"
textbox 3 : "1" then i press button2.
the result is textbox4 display : "C"
other example, if i type textbox1 : "3", textbox2 : "3", textbox3 : "2" then textbox4 diplay "J".
of course, if i type textbox1 : "3", textbox2 : "3", textbox3 : "2" then i'll get msgbox "max for column 2 is 2" or 
if i type textbox1 : "3", textbox2 : "4", textbox3 : "2" i'll get msgbox "max of column 1 is 3"
well, now im stuck, how to filter this. 
thanks before. sorry for bad english.

Answer 1

Hello,
The following uses Lamda and LINQ to query three text box controls where each one has a unique tag value, TextBox1.Tag = 1, TextBox2.Tag = 2, TextBox3.Tag =3. The Tag is used to dictate the order of the columns in the where condition.
In values, a where condition is used to determine any TextBox controls with Text then in the select I create a condition suitable for use in the SQL SELECT. In the variable WhereClause the conditions are combined. There is one or more conditions they are
appended to the SQL statement.
Now if we have to deal with columns of type string we need to surround them in apostrophes which opens up a can or worms if a string contains apostrophes so food for thought.
Code suitable for VS2012 or higher, for VS2010 line continuation is needed.
''' <summary>
''' Each TextBox (three of them) have their tag set to 1,2,3 for ordering columns
''' in the where clause.
''' The Where conditions are using "and", you can also do "or" instead
''' </summary>
''' <remarks></remarks>
Public Class Form1
Private Sub Button1_Click(sender As Object, e As EventArgs) _
Handles Button1.Click
Dim SelectStatement As String = "SELECT * FROM SomeTable"
Dim Values = Me.Controls.OfType(Of TextBox).Where(
Function(tb) Not String.IsNullOrWhiteSpace(tb.Text)).Select(
Function(tb)
Return New Item With
.Index = CInt(tb.Tag),
.Value = tb.Tag.ToString & " = " & tb.Text
End Function).ToList.OrderBy(Function(item) item.Index)
Dim WhereClause = String.Join(" and ",
(From T In Values Select T.Value).ToArray)
If Not String.IsNullOrWhiteSpace(WhereClause) Then
SelectStatement &= " WHERE " & WhereClause
Else
' Nothing to append
End If
Console.WriteLine(SelectStatement)
End Sub
End Class
''' <summary>
''' Strong type data in the select part of the
''' lambda statement above
''' </summary>
''' <remarks></remarks>
Public Class Item
Public Property Index As Integer
Public Property Value As String
Public Sub New()
End Sub
End Class
Please remember to mark the replies as answers if they help and unmark them if they provide no help, this will help others who are looking for solutions to the same or similar problem.