How to Convert string to Generic Of T? - vb.net

Question

How I call generic Of T sub choose form string?
How to better way code like this?
Sub ShowAddfrm(Of T As {Form, New})()
dim frm as new T 'New Form
frm.Show()
End Sub
Private Sub btnAddProblemfrm_Click(sender As Object, e As EventArgs)
Dim keys As String = CType(sender, Button).Name.Replace("btnAdd", "")
If keys = "frmShowProblem" Then
ShowAddfrm(Of frmShowProblem)()
End If
If keys = "frmUser" Then
ShowAddfrm(Of frmUser)()
End If
End Sub

Answer 1

Try this overloaded method, allowing both a Form reference and string parameter.
You can pass the default instance of a Form, naming it directly:
ShowAddfrm(Form2)
or the Form's name:
ShowAddfrm("Form2")
or using a Control's Tag property (or any other source) in an event handler:
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
ShowAddfrm(DirectCast(sender, Control).Tag.ToString())
End Sub
There's a difference:
if you use pass the instance of a Form, only that instance will be created. Meaning, if you use a Button to show the Form and you press the Button multiple times, no new instances will be created. If you close the Form, then a new instance will be shown.
If you use the string version, each time you call this method, a new instance of the Form will be shown, so you can have multiple Forms on screen.
The string version uses Activator.CreateInstance to generate a new instance of a Form using it's name.
Sub ShowAddfrm(Of T As {Form, New})(ByVal form As T)
form.Show()
End Sub
Sub ShowAddfrm(formName As String)
Dim appNameSpace = Assembly.GetExecutingAssembly().GetName().Name
Dim form = CType(Activator.CreateInstance(Type.GetType($"{appNameSpace}.{formName}")), Form)
ShowAddfrm(form)
End Sub