VB-APP: Program freezes when assigning a new datatable to the datagridview

[nev]

Happy Easter to all!

I have a problem with a datagridview. I placed code in a button click event as follows:

dim dtt as datatable = dataset.employees.copy
dtt.DefaultView.RowFilter = "[Last Name]='" & Me.LastNameTextBox.Text & "'"
Me.DataGridView.DataSource = ""
Me.DataGridView.DataSource = dtt

When I run the program, I will be able to filter the datagridview by entering the lastname in the textbox then click the button. But, it only works twice. The third time I enter a new last name in the textbox and click the button, the program will freeze. I was expecting the code to work since I am assigning a new datatable for the datagridview everytime I click the button.

Any help will be very much appreciated. Thank you.

UPDATE 1:
I have traced the problem in the statement:

Me.DataGridView.DataSource = dtt

Does this mean that the way I am removing the datasource as...

Me.DataGridView.DataSource = ""

is incorrect? If so, how should this be done? Thank you.

UPDATE 2:
Hi, I've tried declaring dtt like this but it didn't work...

dim dtt as new datatable
dtt = dataset.employees.copy

[nev]

Any help here? Or any links that anyone can share?

UPDATE 3:
I noticed that the code works (I think). I noticed that the first time I clicked the button it assigns dtt to the datasource pretty fast. The next clicks I do to filter tend to slow down the assigning of dtt as the datasource. Hence, the program not responding. Does anyone know a correct workaround for this? Or any links that explains this behavior? Thank you very much.

UPDATE 4:
Any help here? I'm still stuck at this problem. Thanks.