CODEWITHSUNDEEP
c#variablesmethods
tstokes8040
tstokes8040

Reputation: 71

Possible unintended reference comparison in C#

I am getting an Possible unintended reference comparison; to get a value comparison, cast the left hand side to type 'string' on the if statements in the GetPrice method. It shows its highlighted on all the "if (size == "Small")" statements. Here are my variables:

drinkType = GetDrinkType();
size = GetDrinkSize();
price = GetPrice(size);

private string GetDrinkType()
        {
            string theDrink;
            theDrink = "None Selected";

            if (rdoCoffee.Checked)
            {
                theDrink = "Coffee";
            }
            else if (rdoCoco.Checked)
            {
                theDrink = "Hot Chocolate";
            }
            else if (rdoSmoothie.Checked)
            {
                theDrink = "Smoothie";
            }

            return theDrink;
        }

        private string GetDrinkSize()
        {
            string theSize;
            theSize = "None Selected";

            if (rdoSmall.Checked)
            {
                theSize = "Small";
            }
            else if (rdoMedium.Checked)
            {
                theSize = "Medium";
            }
            else if (rdoLarge.Checked)
            {
                theSize = "Large";
            }
            return theSize;
        }
        private decimal GetPrice(object size)
        {
            decimal thePrice;
            thePrice = 0;
            if (size == "Small")
            {
                thePrice = 1.25m;
            }
            else if (size == "Medium")
            {
                thePrice = 2.50m;
            }
            else if (size == "Large")
            {
                thePrice = 3.35m;
            }
            return thePrice;
        }

Upvotes: 1

Views: 1461

Answers (4)

Roland Mai
Roland Mai

Reputation: 31097

Since in GetPrize, the type of size is object, but you are comparing it to a string with size == "Large".

Change the comparison with "string text".Equals(object) as shown below

private decimal GetPrice(object size)
{
      decimal thePrice = 0m;
      if ("Small".Equals(size))
      {
            thePrice = 1.25m;
      }
      else if ("Medium".Equals(size))
      {
            thePrice = 2.50m;
      }
      else if ("Large".Equals(size))
      {
            thePrice = 3.35m;
      }
      return thePrice;
}

Upvotes: 0

Robert Chumley
Robert Chumley

Reputation: 119

Try changing the "object" in GetPrice to "string".

Upvotes: 1

Thomas Levesque
Thomas Levesque

Reputation: 292555

The size parameter is declared of type object, so the compiler doesn't know it's actually of type string. So it uses the default equality for type object, which is a reference comparison.

If you change the type of size to string, it will use the equality operator overload from the string class, which performs a value comparison.

private decimal GetPrice(string size)

Upvotes: 3

Jevgeni Geurtsen
Jevgeni Geurtsen

Reputation: 3133

The warning occurs because you are comparing a string to an object. If you change

 if (size == "Small")

to

 if (size.ToString() == "Small")

the warning will be removed.

Upvotes: 1

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