"Object Required" when setting Active.Sheet to Range - vba

Question

I have tried about every solution that I could find.
What I am trying to do is run a Function for selected range (The ActiveSheet)
I can't even get to the looping part because it errors on line 5 (arc = ActiveSheet.Row.Count). The error it throws is "Object Required". I have tried several different solutions found online with no luck. I am a complete noob at excel vba (my background is vb.net and c#). I would greatly appreciate a nudge in the right direction on what going wrong. Thanks in advance :)
Sub TestV2()
Dim rng As Range
Dim selectedRange As Range
Dim arc As Range
Set arc = ActiveSheet.Rows.Count
Set selectedRange = ActiveSheet.Rows.Count
For Each rng In selectedRange.Cells
If Application.CalculationState = xlDone Then
FireValidate
End If
Next rng
End
End Sub

Answer 1

You're getting this error because you declared arc as Range but you are trying to assign a Long number to it.

Answer 2

The Set keyword is required in VBA, to assign object references.
Set arc = ActiveSheet.Rows.Count
Set selectedRange = ActiveSheet.Rows.Count
Both arc and selectedRange are declared As Range, which is an object type - so the Set keyword is correct.
The problem is with the expressions on the right-hand side of the assignment operator: ActiveSheet.Rows.Count evaluates to a Long integer, which is not an object type. ActiveSheet.Rows.Count gets you the number of rows on the ActiveSheet, ...which should be the same number regardless of what specific sheet is currently active (all sheets have the same number of rows).
Hence, object required: you can't legally assign a Range object reference to a Long integer value; you need the right-hand side expression to evaluate to an object reference.
Tim Williams' answer shows how you can correctly assign the selectedRange to the Application.Selection, assuming what's currently selected is a Range object (a type mismatch error will occur if that's not the case).
What I am trying to do is run a Function for selected range (The ActiveSheet)
ActiveSheet doesn't return the selected range - it gives you the sheet that's currently active.
I am a complete noob at excel vba (my background is vb.net and c#)
You can reference the Excel object model from VB.NET or C# as well, and automate Excel through Visual Studio Tools for Office (VSTO) if you're more comfortable with these more powerful .net languages - but the object model will behave identically.

Answer 3

If you just want the current selection then:
Set selectedRange = Selection

Answer 4

You could try to modify your code as follows:
Sub TestV2()
Dim rng As Range
For Each rng In Selection
If Application.CalculationState = xlDone Then
FireValidate
End If
Next rng
End Sub
Hopefully it helps you.

Answer 5

There are three errors in your code:
.1. The key error. Use ActiveSheet.Rows.Count directly may encounter "Object Required" exception, instead, you can use the following worked code:
Dim ws As Worksheet
Set ws = ActiveSheet
'MsgBox ws.Rows.Count
Set arc = ws.Rows.Count
As hod said(this is not the key issue, but need to fix),
You're getting this error because you declared arc as Range but you are trying to assign a Long number to it.
As William have pointed, you can use the Set selectedRange = Selection directly if you want to operate the selected range.
Sub TestV2()
Dim rng As Range
Dim selectedRange As Range
Set selectedRange = Selection
For Each rng In selectedRange.Cells
If Application.CalculationState = xlDone Then
'FireValidate
'MsgBox "OK"
End If
Next rng
End Sub
And I think most time we just need the UsedRange.Rows but not the Rows all.
ActiveSheet.UsedRange.Rows.Count for the current sheet.
Worksheets("Sheet name").UsedRange.Rows.Count for a specific sheet.