How to filter unbound datagridview with textbox vb.net? - vb.net

Question

I'm a complete rookie. I learned so much from here but this one I can't find the answer to. I'm using Visual Studio Pro 2015.
I have a windows form application that has a single column datagridview that is populated by reading a textfile, line by line at runtime. Each time the contents of the textfile will be different.
I want the user to be able to filter the list in the datagridview by entering characters in a textbox. The data is not "bound" to the datagridview, because at this point I don't know if that is necessary, and I don't completely understand it.
This is the code that I have for loading the datagridview, and the textbox is called txtFilter.
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
'read all lines from the file into a string array (one line per string)
Dim lines() As String = My.Computer.FileSystem.ReadAllText("c:\list_in.txt").Replace(vbLf, "").Split(vbCr)
Dim dgrow As DataGridViewRow
Dim dgcell As DataGridViewCell
'insert each line of input into a row in the datagrid
For Each line As String In lines
dgrow = New DataGridViewRow
dgcell = New DataGridViewTextBoxCell
If line <> "" Then
dgcell.Value = line
dgrow.Cells.Add(dgcell)
DataGridView1.Rows.Add(dgrow)
End If
Next
DataGridView1.Columns("ObjectName").ReadOnly = True
DataGridView1.ClearSelection()
End Sub

Answer 1

Edit:
Looking at your solution, I would advise you execute Dim lines() As String = My.Computer.FileSystem.ReadAllText("c:\list_in.txt").Replace(vbLf, "").Split(vbCr) outside of the txtFilter_TextChanged sub, as otherwise you are importing the entire list every time the user enters a key, which is unnecessary. If the list may change while the user is using the program, I'd instead recommend adding a 'refresh' button, especially if your text file could be a long one.
You also added a couple lines of code to remove the sound when the user presses the Enter key. If the user is expected to press the enter key to search, then you don't need to update the DataGridView every time the user enters a new character in the textbox. This would be easier on memory, and again very beneficial if you have a large text file.
I'm sure there's an easier way, but here's my approach.
Private Sub txtFilter_TextChanged(sender As Object, e As EventArgs) Handles txtFilter.TextChanged
Dim searchedlines(-1) As String 'create an array to fill with terms that match our search
If txtFilter.Text = Nothing Then
datapopulate(lines) 'just populate the datagridview with our text file array
Else
For Each line In lines
If line Like "*" & txtFilter.Text & "*" Then 'check if anything in our search matches any of our terms
ReDim Preserve searchedlines(UBound(searchedlines) + 1) 'resize the array to fit our needs
searchedlines(UBound(searchedlines)) = line 'add the matched line to our array
End If
Next
datapopulate(searchedlines) 'populate the datagrid with our matched terms array
End If
End Sub
Private Sub datapopulate(ByVal mylist)
Dim dgrow As DataGridViewRow
Dim dgcell As DataGridViewCell
DataGridView1.Rows.Clear() 'clear the grid
For Each line As String In mylist 'do the same thing here that we did on form load
dgrow = New DataGridViewRow
dgcell = New DataGridViewTextBoxCell
dgcell.Value = line
dgrow.Cells.Add(dgcell)
DataGridView1.Rows.Add(dgrow)
Next
End Sub
What I did is created a sub that handles whenever the text in txtFilter is changed. Alternatively, you could run that code in a sub that handles a button click. Given that, from what I know, ReDim can be a costly item in terms of memory usage, if your text document was hundreds of lines long, you might want it on a button click instead. You could probably use a list, but I haven't played around enough to know how to go about doing that.
An important note: in order for the sub txtFilter_TextChanged to be able to see lines(), I defined it outside of a sub but inside of your main class, so that all subs could access it, like so:
Public Class Form1
Dim lines() As String = My.Computer.FileSystem.ReadAllText("c:\list_in.txt").Replace(vbLf, "").Split(vbCr)
'...subs here...
End Class
I hope this helps you get started!

Answer 2

I have a solution working. Thank you very much.
Private Sub txtFilter_TextChanged(sender As Object, e As EventArgs) Handles txtFilter.TextChanged
'read all lines from the file into a string array (one line per string)
Dim lines() As String = My.Computer.FileSystem.ReadAllText("c:\list_in.txt").Replace(vbLf, "").Split(vbCr)
Dim dgrow As DataGridViewRow
Dim dgcell As DataGridViewCell
DataGridView1.Rows.Clear()
'insert each line of input into a row in the datagrid
For Each line As String In lines
dgrow = New DataGridViewRow
dgcell = New DataGridViewTextBoxCell
If line.Contains(txtFilter.Text) Then
dgcell.Value = line
dgrow.Cells.Add(dgcell)
DataGridView1.Rows.Add(dgrow)
End If
Next
DataGridView1.Columns("ObjectName").ReadOnly = True
DataGridView1.ClearSelection()
End Sub
And I also found this to eliminate the bell from ringing when the user pressed the enter key when entering the filter text.
Private Sub txtFilter_KeyPress(sender As Object, e As KeyPressEventArgs) Handles txtFilter.KeyPress
' this keeps the bell from ringing when the user presses the 'enter' key
If Asc(e.KeyChar) = 13 Then
e.Handled = True
End If
End Sub