Insted of writing seperate code for Search on Button just write your code on TextBox KeyDown Event and Check Whether Enter Key Pressed or Not.If User Press Enter Key then Execute Your Code.Example :
Private Sub TextBox1_KeyDown(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles TextBox1.KeyDown
If e.KeyCode = Keys.Enter Then
End If
End Sub