default value for generic type in c#

The docs for Dictionary.TryGetValue say:

When this method returns, [the value argument] contains the value associated with the specified key, if the key is found; otherwise, the default value for the type of the value parameter. This parameter is passed uninitialized.

I need to mimic this in my class. How do I find the default value for type T?

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Exact duplicate of Returning a default value. (C#)