How add key to dictionary without value?

Question

in normally we should add key and value together in dictionary type. like:

myDict.Add(key1, value1);
myDict.Add(key2, value2);

I want to know, Is there any way to add key first, then insert its value? (not both of them at the same time)

Answer 1

If the value type of the dictionary is nullable, you could add a null value:

myDict.Add(key1, null);

If the value is non nullable, you can use a default value, either default or some out of range value, depending on your expected meaningful values.

myDict.Add(key1, default(int));
myDict.Add(key1, Int32.MinValue);

But

as mentioned in the comments, there is no discernible merit in doing this. You can add values at any time, there is no need to pre-initialize a dictionary with keys.