creating a class in C#, use of unassigned variable

I recieve a "use of unassigned varable in InfoPeople". I am not sure why, my class is set up as the example in the textbook. Could someone shed a little light on this. Thanks.

  class personInfo
    {
        public string fName;
        public string lName;
        public int personID;
    }
    class Program
    {
        static void Main(string[] args)
        {
            personInfo InfoPeople;
            InfoP开发者_Go百科eople.fName = "jeff";
            Console.WriteLine("the fName is: " + " " + InfoPeople.fName);
        }
    }

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You haven't initialised your instance:

personInfo InfoPeople = new personInfo();

I would try and conform to C# style type/casing conventions:

PersonInfo infoPeople = new PersonInfo();

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You need to new your object instance like this:

personInfo InfoPeople = new personInfo();

That's just the C# syntax for creating new object instances.

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It doesn't work because InfoPeople is a variable that holds a reference to a personInfo, but you never actually created a personInfo.

Fix it by saying:

personInfo InfoPeople = new personInfo();

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By the way, your naming convention isn't very conventional. People generally PascalCase class names and camelCase variables. Try to follow that convention so that your code is easier to understand.

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In C#, you must assign a value to a local variable before it is used -- local variables do not default to anything (not even the default value of the type!).

As others have pointed out, the correct solution is likely to use a new personInfo(). However, just assigning null to the InfoPeople variable (above where it is used) will get rid of the compile-time error (and get a NullReferenceException at run-time ;-)

(That is, the compiler error has nothing to do with InfoPeople containing an "invalid" value -- it only cares that some value has been previously assigned.)

Happy coding.

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Extra tip:

// C# allows one to instantiate a new object
// and assign members at the same time.
personInfo InfoPeople = new personInfo {
    fName = "jeff",
};

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change you first line in main() function as below. You specified the object type with "personInfo InfoPeople" statement but did not allocate memory. When you do that with 'new()' keyword, it actually creates object in memory, and that is what the error for.

personInfo InfoPeople = new personInfo()

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You declare the local variable of type personInfo named InfoPeople, but you don't assign a value to it before trying to use it. The compiler can prove this and therefore it complains. Simple enough.

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Have to instantiate an instance of personInfo

  class personInfo
{
    public string fName;
    public string lName;
    public int personID;
}
class Program
{
    static void Main(string[] args)
    {
        personInfo InfoPeople = new personInfo();
        InfoPeople.fName = "jeff";
        Console.WriteLine("the fName is: " + " " + InfoPeople.fName);
    }
}

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You didn't set InfoPeople to a new instance of personInfo:

personInfo InfoPeople = new personInfo();

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Don't you need to instantiate that as new?

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"New personInfo" you have to instantiate the object from the class