Should IDisposable.Dispose() be made safe to call multiple times?

c# .net idisposable
Jake Petroules picture Jake Petroules · Mar 15, 2011 · Viewed 11.9k times · Source

Should implementations of IDisposable make Dispose() safe to call multiple times? Or the opposite? What approach to most .NET Framework classes take?

Specifically, is it safe to call System.Data.Linq.DataContext.Dispose() multiple times?

The reason I ask is because I am wondering if this extra protection is necessary:

public override void Dispose(bool disposing)
{
    // Extra protection...
    if (this.obj != null)
    {
        this.obj.Dispose();
        this.obj = null;
    }

    // Versus simply...
    this.obj.Dispose();

    base.Dispose(disposing);
}

when disposing IDisposable members of a class, or whether I should just call this.obj.Dispose() without concern for whether it has been previously called.

Answer

Adam Robinson picture Adam Robinson · Mar 15, 2011

You should be safe to call it more than once, though you should probably avoid it if you can.

From the MSDN page on IDisposable.Dispose():

If an object's Dispose method is called more than once, the object must ignore all calls after the first one. The object must not throw an exception if its Dispose method is called multiple times.

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