I would like to create dictionary with keys only. For example:
Dictionary <string, double> SmplDict= new Dictionary<string, double>();
SmplDict.Add("KeyOne");
SmplDict.Add("KeyTwo");
Of course, I can initialize with some predefined values, but this values will be overwritten, so I want only keys declared for now. I tried
SmpDict.Add("KeyOne", null)
but it did not work.
You can't put null value where double value is expected, as it is not a reference-type but a value-type:
Dictionary <string, double>
Instead, put 0:
SmpDict.Add("KeyOne", 0)
On the other hand, if you want to keep put nulls, mark your double value as nullable:
Dictionary <string, double?>
You have to make it nullable, if you want to put null:
Dictionary <string, double?> SmplDict= new Dictionary<string, double?>();
Now you can add null as value:
SmpDict.Add("KeyOne", null)
Dictionary<string, double?> smplDict = new();
smplDict.Add("KeyOne", default);
smplDict.Add("KeyTwo", default);
I would mention that it might be that you are doing something wrong that this is your need. Maybe you can use some other collection that is more suitable, e.g: HashSet<T>.
If you want your values to be null then choose a type that can be nullable for the Value.Such as double?, object etc...
While a double can't be null there is a Not-a-Number constant:
Dictionary <string, double?> SmplDict= new Dictionary<string, Double.NaN>();
for which you can check..
