C# : 'is' keyword and checking for Not

Question

This is a silly question, but you can use this code to check if something is a particular type...

if (child is IContainer) { //....

Is ther

Answer 1

if(!(child is IContainer))

is the only operator to go (there's no IsNot operator).

You can build an extension method that does it:

public static bool IsA(this object obj) {
    return obj is T;
}

and then use it to:

if (!child.IsA())

And you could follow on your theme:

public static bool IsNotAFreaking(this object obj) {
    return !(obj is T);
}

if (child.IsNotAFreaking()) { // ...

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Update (considering the OP's code snippet):

Since you're actually casting the value afterward, you could just use as instead:

public void Update(DocumentPart part) {
    part.Update();
    IContainer containerPart = part as IContainer;
    if(containerPart == null) return;
    foreach(DocumentPart child in containerPart.Children) { // omit the cast.
       //...etc...