Dispose method in VB.NET form's designer file

Question

<System.Diagnostics.DebuggerNonUserCode()> _
Protected Overrides Sub Dispose(ByVal disposing As Boolean)
    Try
        If disposing AndAlso components IsNot Nothing Then
            components.Dispose()
        End If
    Finally
        MyBase.Dispose(disposing)
    End Try

Can anybody please tell me why we use this in designer.vb?

Answer 1

Dispose is used to free resources that are not managed by the runtime (unmanaged resources). This include files, streams, fonts, etc. The garbage collector automatically releases the memory allocated to a managed object when that object is no longer used. However, it is not possible to predict when garbage collection will occur. Furthermore, the garbage collector has no knowledge of unmanaged resources such as window handles, or open files and streams.

In your code, the base class's Dispose method is overridden by the child class implementation, hence the overriden keyword the call to Mybase.Dispose. The base class is IContainer and the child class is Form. The Dispose method is available in the IDisposable interface.

In designer.vb, this auto generated code serves to call Dispose on the components of the form when Dispose is called on the form i.e. when the form is being disposed, dispose its components as well.

<System.Diagnostics.DebuggerNonUserCode()> _
Protected Overrides Sub Dispose(ByVal disposing As Boolean)
    Try
        ' If Dispose() has been called explicitly free both managed and 
        ' unmanaged resources (disposing = true)
        ' and there are components in the form
        If disposing AndAlso components IsNot Nothing Then 
            ' Free the resources used by components
            components.Dispose()
        End If
    Finally
        ' Once done disposing the current form's resources, 
        ' dispose the resources held by its base class 
        ' Finally clause executes this code block (to dispose base class)
        ' whether or not an exception has been encountered while 
        ' disposing the resources in the form
        MyBase.Dispose(disposing)
    End Try

More information

• Form.Dispose Method (Boolean)
• Implementing Finalize and Dispose to Clean Up Unmanaged Resources
• What's that "Windows Form Designer generated code" anyway?
• C# Finalize/Dispose pattern
• Dispose vs Dispose(bool)