CODEWITHSUNDEEP
c#classfunctionforeachnull
cubician
cubician

Reputation: 19

Function always returns null?

This function always returns null. sString is a class with a string "Name" and string "Value" values. Don't ask why I'm not using a regular string-- it's complicated. here's my function:

static string Get_sString(string VarName, ref List<sString> VarList)
{
    foreach (sString TestsString in VarList)
    {
        if (TestsString.Name == VarName)
        {
            return TestsString.Name;
        }
    }
    return null;
}

It's supposed to return the instance with the same Name value as VarName, and it works, except for the if statement always is false. I can't figure out why. I actually have an almost identical class called sDecimal, where the only difference is the Value property is a decimal, not a string. The Get_sDecimal() works perfectly fine with that, and the only difference between Get_sDecimal() and Get_sString() are that one tests sDecimal and one tests sString. Thanks!

EDIT: Here's sString Class.

class sString
{
    public string Name;
    public string Value;

    /// <summary>
    /// String Value variables that may have the same name.
    /// </summary>
    /// <param name="n">Internal name of variable.</param>
    /// <param name="v">Value of variable.</param>
    public sString(string n, string v)
    {
        Name = n;                    
        Value = v;                    
    }
}

EDIT: Here's some output code (and output) to clear things up.

static string Get_sString(string VarName, ref List<sString> VarList)
        {
            foreach (sString TestsString in VarList)
            {
                Console.WriteLine("Looking for: " + VarName);
                Console.WriteLine("Comparing with: " + TestsString.Name);
                if (TestsString.Name == VarName)
                {
                    Console.WriteLine("Match!");
                    return TestsString.Name;
                }
            }
            return null;
        }

Here's the output:

Looking for: Q
Comparing with: Q

EDIT: I added a couple more variables to the list. Here's the new output:

Looking for: Q
Comparing with: Q
Looking for: Q
Comparing with: Z
Looking for: Q
Comparing with: VariableX

Still no Match.

Upvotes: 0

Views: 233

Answers (3)

Suresh Kumar Veluswamy
Suresh Kumar Veluswamy

Reputation: 4353

You should use String.Equals instead of == operator.

== operator does not always work. you can find samples in the thread Are string.Equals() and == operator really same?.

Upvotes: 1

Matt Johnson-Pint
Matt Johnson-Pint

Reputation: 241420

You do realize that you have basically re-implemented LINQ:

return VarList.FirstOrDefault(x=> x.Name == VarName);

Also your sString class could just be a KeyValuePair<string,string>

UPDATE

Actually, you said:

It's supposed to return the instance with the same Name value as VarName

But it doesn't return an sString instance. Instead, it returns TestsString.Name - which is the same string you started with, but only if it's in the list. So basically, this is a complicated "contains" check.

Upvotes: 2

Marc Gravell
Marc Gravell

Reputation: 1062502

The code fundamentally works:

var list = new List<sString>
{
    new sString("foo", "123"),
    new sString("bar", "456")
};
var s = Get_sString("foo", ref list);
// = "foo", not null

Don't get me wrong - I'd change every line of it. But it doesn't always return null.

Brief problem list:

  • public fields
  • unnecessary ref
  • could just use Dictionary<string,string>
  • horrible names
  • I wonder if you should be returning .Value rather than .Name

Upvotes: 6

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