CODEWITHSUNDEEP
.netvb.netwinforms
xpda
xpda

Reputation: 15813

Dispose a user control in Closing or Closed event?

I have a user control with bitmaps that should be disposed when the form closes. Is it better to do this in the form's Closing event, Closed event, or somewhere else?

Part 2: Inside a user control, when its form closes, should a bitmap be disposed in the Disposed event or somewhere else?

Upvotes: 1

Views: 1200

Answers (1)

Hans Passant
Hans Passant

Reputation: 941465

No, the form has no business messing with private members of the user control. The universal .NET rule applies here as well, a class needs to dispose its members in its own Dispose() method. It will run automatically when the form closes, no assistance is needed.

There's a quirk however, the project item template for UserControl is awkward. It puts the Dispose() method inside the control's Designer.cs file. Best thing to do is to cut+paste this method into the control's main source file. After you edited the method, it ought to resemble this:

    /// <summary> 
    /// Clean up any resources being used.
    /// </summary>
    /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
    protected override void Dispose(bool disposing) {
        someBitmap.Dispose();             // <== added
        someOtherBitmap.Dispose();
        if (disposing && (components != null)) {
            components.Dispose();
        }
        base.Dispose(disposing);
    }

Some programmers really dislike tinkering with the Designer.cs file, do note that there's nothing to worry about since the code is outside the #region marked Component Designer generated code. The alternative is to use the Disposed event:

    public UserControl1() {
        InitializeComponent();
        this.Disposed += UserControl1_Disposed;
    }

    void UserControl1_Disposed(object sender, EventArgs e) {
        someBitmap.Dispose();
        someOtherBitmap.Dispose();
    }

Upvotes: 5

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