Question

I have the following:

KeyValuePair<string, string>? myKVP;
// code that may conditionally do something with it
string keyString = myKVP.Key;  
// throws 'System.Nullable<System.Collections.Generic.KeyValuePair<string,string>>' 
// does not contain a definition for 'Key'

I’m sure there is some reason for this as I can see that the type is nullable. Is it because I am trying to access the key when null could cause bad things to happen?

Answer 1

Try this instead:

myKVP.Value.Key;

Here is a stripped down version of System.Nullable<T>:

public struct Nullable<T> where T: struct
{
    public T Value { get; }
}

Since the Value property is of type T you must use the Value property to get at the wrapped type instance that you are working with.

Edit: I would suggest that you check the HasValue property of your nullable type prior to using the Value.

if (myKVP.HasValue)
{
    // use myKVP.Value in here safely
}