如何通过字符串从其他项目/程序集打开表单？

Question

如何通过字符串从不同的项目/程序集中打开表单？

在一个解决方案中我有很多项目
例如：

1. SalePurchase：具有：FrmSale，FrmPurchase，FrmMRN等...
   
2. FAS：具有：FrmPayment，FrmReceipt等...
3. 等...

我想从FAS.FrmPayment项目中打开SalePurchase

位于SalePurchase中的功能下方

Public Shared Function CreateForm(ByVal formName As String) As Form
    Return DirectCast(CreateObjectInstance(formName), Form)
End Function

Public Shared Function CreateObjectInstance(ByVal objectName As String) As _
Object
    Dim obj As Object : Dim ObjName As String = objectName
    Try
        If objectName.LastIndexOf(".") = -1 Then
            objectName = [Assembly].GetExecutingAssembly.GetName.Name & "." & objectName
        End If
        obj = [Assembly].GetExecutingAssembly.CreateInstance(objectName)
    Catch ex As Exception
        obj = Nothing
    End Try : Return obj
End Function

我运行SalePurchase项目

当我通过String=FrmSale时，效果很好

Dim FrmOpen As Form : FrmOpen =CreateForm(FrmSale)
FrmOpen.MdiParent = parent : FrmOpen.Show() : FrmOpen.Focus()

‘In this case obj has value {SalePurchase.FrmSale}

我通过String=FrmPayment时引发错误Object Reference not set to an Instance of an object

Dim FrmOpen As Form : FrmOpen =CreateForm(FrmPayment)
FrmOpen.MdiParent = parent : FrmOpen.Show() : FrmOpen.Focus()
‘In this case obj has value Nothing

Dim FrmOpen As New FrmPayment 'use direct object
FrmOpen.MdiParent = parent : FrmOpen.Show() : FrmOpen.Focus()
‘This is work fine

如何通过传递字符串打开FrmPayment？