CODEWITHSUNDEEP
c#winforms
cristi.gherghina
cristi.gherghina

Reputation: 321

Warning 1 Possible unintended reference comparison; to get a value comparison, cast the left hand side to type 'string'

I read from a text file . in that text file a line is with YES or NO (yes if it's correct, no if it's not)

I used at the beginning answer.Tag = "NO;" then when I press a button it goes answer.Tag = "YES";

I have a verify button which does 

if (answer[0].Tag == "bla bla" && answer[1].Tag== "blabla2")
{
    MessageBox.Show("They Match");
}
else 
    MessageBox.Show("They don't");

Then I have this problem : Warning 1 Possible unintended reference comparison; to get a value comparison, cast the left hand side to type 'string'

I don't know why it doesn't do the comparison . It skips to else

Upvotes: 1

Views: 11413

Answers (3)

Alex
Alex

Reputation: 23300

The Possible unintended reference comparison is this one:

answer[1].Tag == "blabla2"

The Tag is an object, you are allowed to compare it to "blabla2" because string is a reference type. The compiler is "casting" your string to object and is performing a reference comparison (which will evaluate to false since they are not the same object).

To fix this, you have to cast Tag before checking. Together with the fix I mentioned above, your code would become

if (answer[0].Tag.ToString() == "bla bla" && answer[1].Tag.ToString() == "blabla2")
{
    MessageBox.Show("They Match");
}
else 
    MessageBox.Show("They don't");

Upvotes: 4

Sriram Sakthivel
Sriram Sakthivel

Reputation: 73492

Usually Tag property will be of type Object, so I assume it is of type Object. == operator with System.Object work as reference comparison (meaning references of the instances are compared than value).

To fix it just introduce a cast to string.

if ((string)answer[0].Tag == "bla bla" && (string)answer[1].Tag== "blabla2")
{
    MessageBox.Show("They Match");
}
else
{
    MessageBox.Show("They don't");
}

Upvotes: 0

Ahmed ilyas
Ahmed ilyas

Reputation: 5822

correction of your code:

if (answer[0].Tag == "bla bla" && answer[1].Tag== "blabla2")
{
    MessageBox.Show("They Match");
}
else 
    MessageBox.Show("They don't");

here specifically in your if condition:

if (answer[0].Tag **==** "bla bla" && answer[1].Tag== "blabla2")

should be 2 equals signs, not one

Upvotes: 0

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