“String may be null here” but I don't think it can be null

Question

So I wanted to make a sort of “name checker” that’s always had the first letter be capital and the rest lowercase. I got that to work but whenever I got past the name checker and wanted to use the name in future code, it would always say “string may be null here.” I have tried many things like adding a ? But nothing works. I don’t think it can be null but maybe I’m wrong. Here is my code here:

class Program
{
    static void Main()
    {
        string? name, choice;
        bool finishnameingcharacter;
        finishnamingcharacter = true;
        while(finishingnamingcharacter == false)
        {
             Console.WriteLine("Enter your name");
             name = Console.ReadLine();
             name = name?.ToLower();
             if(name != null)
             {
                 name = char.ToUpper(name[0]) + name.Substring(1);
             }
             Console.WriteLine("");
             Console.WriteLine("Your name is " +name+ ", is that correct?");
             Console.WriteLine("");
             Console.WriteLine("1: Yes");
             Console.WriteLine("2: No");
             choice = Console.ReadLine();
             if(choice == "1")
             {
                 finishnamingcharacter = 1;
             }
             if(choice == "2")
             {
                 Console.WriteLine("");
             }
             else
             {
                 Console.WriteLine("Invalid Claim")
             }
        }
        Console.WriteLine(name);
    }
}

The "name" at the bottom is where the error is. If there's any confusion about my question ask me. I tried my best to explain it.

Answer 1

Why use a nullable string in this software?

You didn't initialize the name at the beginning, if your loop will never run, then the name output line will be NULL. This is what your error points to.

It is better to initialize variables before their first use, as they can be NULL by default (valid for reference types such as classes). For a string, one option would be String.Empty

string name = String.Empty, choice = String.Empty;

These two lines can be combined:

 bool finishnameingcharacter;
 finishnamingcharacter = true;

 // Replaced by
 bool finishnameingcharacter = true;

On the next line in the while loop, you check the condition: finishingnamingcharacter == false. The loop checks the condition and only then executes. To execute the loop, you need the condition to be TRUE, but it will not take this value, because earlier you defined the variable finishnamingcharacter = true. true != false. By default you need to define this variable as false

bool finishnameingcharacter = false;

The user can enter an empty string value, so converting it to lowercase immediately doesn't matter, as long as it checks for an empty string. There is a special method for checking if a string is empty: string.IsNullOrEmpty() - it returns true if the string is empty or null. If the user entered the wrong name, then we need to ask him to enter again, for this, the continue operator is used.

name = Console.ReadLine();
if(string.IsNullOrEmpty(name) || string.IsNullOrWhiteSpace(name))
{
    Console.WriteLine("Sorry, your name is empty. Please enter again.")
    continue;
}
//So if name is not empty: jOhN
name = name.ToLower(); //john
name = char.ToUpper(name[0]) + name.Substring(1); //John

For boolean values it is better to use reserved words, i.e. instead of finishnamingcharacter = 1 it is better to write finishnamingcharacter = true

Rest of the code looks good. We all took the first steps :)

Full modified code here:

class Program
{
    static void Main()
    {
        string name = String.Empty choice = String.Empty;
        bool finishnameingcharacter = false;

        while(finishingnamingcharacter == false)
        {
            Console.WriteLine("Enter your name");
            name = Console.ReadLine();
            if(string.IsNullOrEmpty(name) || string.IsNullOrWhiteSpace(name))
            {
                Console.WriteLine("Sorry, your name is empty. Please enter again.")
                continue;
            }
            //So if name is not empty: jOhN
            name = name.ToLower(); //john
            name = char.ToUpper(name[0]) + name.Substring(1); //John

            Console.WriteLine("");
            Console.WriteLine("Your name is " +name+ ", is that correct?");
            Console.WriteLine("");
            Console.WriteLine("1: Yes");
            Console.WriteLine("2: No");
            choice = Console.ReadLine();

            if(choice == "1")
            {
                finishnamingcharacter = true;
            }
            else if(choice == "2")
            {
                Console.WriteLine("");
            }
            else
            {
                Console.WriteLine("Invalid Claim")
            }
        }

        Console.WriteLine(name);
    }
}

PS There is a special method TextInfo.ToTitleCase() "wAr aNd pEaCe to titlecase: War And Peace" - I advise you to read

Answer 2

I could not compile your code, so I made some changes

static void Main()
{
    var name = string.Empty;
    var choice = string.Empty;
    do 
    {
        Console.WriteLine("Enter your name");
        name = Console.ReadLine();
        name = name?.ToLower();
        if (name != null && name.Length>1)
                name = char.ToUpper(name[0]) + name.Substring(1);
        
        Console.WriteLine("");
        Console.WriteLine("Your name is " + name + ", is that correct?");
        Console.WriteLine("");
        Console.WriteLine("1: Yes");
        Console.WriteLine("2: No");
        choice = Console.ReadLine();
        if (choice == "1") break;
        
        if (choice == "2")Console.WriteLine("");
        else Console.WriteLine("Invalid Claim");
    
        } while (true);
        
    Console.WriteLine(name);
}