'ReadOnly' variable cannot be the target of an assignment in a lambda expression inside a constructor

You have referred to a ReadOnly variable from within a lambda expression, which is not permitted. The following code causes this error by sending the ReadOnly variable m as the argument to a ByRef parameter.

Class Class1  
  
    ReadOnly m As Integer  
  
    Sub New()  
        ' The use of m triggers the error.  
        Dim f = Function() Test(m)  
    End Sub  
  
    Function Test(ByRef n As Integer) As String  
    End Function  
  
End Class  

Error ID: BC36602

To correct this error

• If possible, change parameter n in function Test to a ByVal parameter, as shown in the following code.

  Class Class1Fix1  
  
      ReadOnly m As Integer  
  
      Sub New()  
          Dim f = Function() Test(m)  
      End Sub  
  
      Function Test(ByVal n As Integer) As String  
      End Function  
  
  End Class  
  

• Assign the ReadOnly variable m to a local variable in the constructor, and use the local variable in place of m, as shown in the following code.

  Class Class1Fix2  
       ReadOnly m As Integer  
  
      Sub New()  
          Dim temp = m  
          Dim f = Function() Test(temp)  
      End Sub  
  
      Function Test(ByRef n As Integer) As String  
      End Function  
  
  End Class  
  

See also

• Lambda Expressions
• ReadOnly
• Constructors