First statement did not work on dictionary result

December 27, 2022

I have a method that returns a dictionary as:

 public async Task<Dictionary<DateTime, double>> GetAvailableTimeOffWithExpiration(int userId)
        {
            ..../ code here

            Dictionary<DateTime, double> expirationDates = ...
            return expirationDates;
        }

Then I want to assign the first value of the dictionary to my DateTime variable of TimeOffApproved model as:

  var timeOffWithExpiration = await this.GetAvailableTimeOffWithExpiration(u.Id);
  var TimeOff = new TimeOffApproved()
                {
                    ExpirationDate = timeOffWithExpiration.First()
                };

But it is returning error:

Error CS0029: Cannot implicitly convert type
‘System.Collections.Generic.KeyValuePair<System.DateTime, double>’ to
‘System.DateTime’

Why is trying to assign the dictionary if I’m using the First() statement?

>Solution :

The First() method returns the first element of a collection in case of the Dictionary that is a KeyPair Value. To get date part you need to add .Value or .Key (depending on the part you need – in your case .Key) to the statement like this:

var timeOffWithExpiration = await this.GetAvailableTimeOffWithExpiration(u.Id);
var TimeOff = new TimeOffApproved()
{
   ExpirationDate = timeOffWithExpiration.First().Key
};

I would recommend a check to ensure that the first element is not null, like this for example (correction due to compiler error):

var timeOffWithExpiration = await this.GetAvailableTimeOffWithExpiration(u.Id);
var TimeOff = new TimeOffApproved()
{
    ExpirationDate = timeOffWithExpiration.Any() ? timeOffWithExpiration.First().Key : new DateTime()
};