Main: Not All Code Paths Return a Value

C# compiler error: not all code paths return a value

You're missing a return statement.

When the compiler looks at your code, it's sees a third path (the else you didn't code for) that could occur but doesn't return a value. Hence not all code paths return a value.

For my suggested fix, I put a return after your loop ends. The other obvious spot - adding an else that had a return value to the if-else-if - would break the for loop.

public static bool isTwenty(int num)
{
    for(int j = 1; j <= 20; j++)
    {
        if(num % j != 0)
        {
            return false;
        }
        else if(num % j == 0 && num == 20)
        {
            return true;
        }
    }
    return false;  //This is your missing statement
}

Main: not all code paths return a value

Return something at the end of Main. Like this:

public static int Main()
{
     List<DocPart> Parts = new List<DocPart>();
     var doc = new DocConfig();
     doc.Description = "bla bla";
     doc.Parts = new List<DocPart>();
     doc.Parts.Add(new DocPart { Title = "aaa", TexLine = @"\include{aaa.tex}" });
     doc.Parts.Add(new DocPart { Title = "bbb", TexLine = @"\include{bbb.tex}" });
     foreach (DocPart part in doc.Parts)
     {
           Console.WriteLine(part.Title);
           {
                 Console.ReadLine();
                 return 0;
           }
     }

     return -1;
}

How to fix the issue not all the code paths return value?

I'm not sure why tslint is complaining, but you can write the whole thing way more elegant as:

return str.split(",").every(el => List.includes(el));

or ES6:

return str.split(",").every(el => List.indexOf(el) > -1);

C# error: not all code paths return a value

Your method SearchFiles only returns a value if isIdentical is false. If it's true, the method never returns.

To remove this error, write something like this:

public static Boolean SearchFiles(string path1, string path2)
{
    // do some work to assign a value to isIdentical
    // note that it would be idiomatic to just write "return isIdentical;" in this case
    // I keep it explicitly here for demonstration purposes 
    if (isIdentical == false)
    {
        return false;
    }
    else
    {
        return true;
    }
}

To your second question: If you declare your method as public static void you must not return any value. void means that the method will not give you anything back.

You might want to have a look at this: Methods (C# Programming Guide), especially the part about return values.

Edit: Since you have your if / else in a foreach loop, you need something like this:

public static Boolean SearchFiles(string path1, string path2)
{
    foreach(var item in collection)
    {
        // do some work to assign a value to isIdentical
        if (isIdentical == false)
        {
            return false;
        }
        else
        {
            return true;
        }
    }
    // in case the collection is empty, you need to return something
    return false;
}

Task return type gives not all code paths return a value

Needs a return :

 return Task.Factory.StartNew(() => { Console.WriteLine("Hello Task library!"); });

Or better:

return Task.Run(() => { Console.WriteLine("Hello Task library!"); });

Error message: not all code paths return a value

You don't have to call return on each conditional statement. Simply track the state with a variable (purchaseState). It is unclear what should happen when a InAppBillingPurchaseException is thrown. I would at least log this error.

public async Task<bool> TestMakePurchase(string productId, string payload)
{   
    var purchaseSuccesful = false;
    var billing = CrossInAppBilling.Current;
    try
    {                                   
        if (await billing.ConnectAsync())
        {                 
            var purchase = await billing.PurchaseAsync(productId, ItemType.InAppPurchase, payload);
            purchaseSuccesful = purchase != null;
        }
    }
    catch (InAppBillingPurchaseException purchaseEx)
    {
        //log this error?
    }
    finally
    {
        await billing.DisconnectAsync();
    }

    return purchaseSuccesful;
}

Not all code paths return a value - C#

your methods return type is List<Employee>. It expects you to return a List<Employee> object. But you are not returning anything from your method of type List<Employee>.

following will fix your issue.

public List<Employee> GetEmployees()
    {
        List<Employee> employees = new List<Employee>();
        Employee emp = new Employee();
        emp.FirstName = "johnson";
        emp.LastName = " fernandes";
        emp.Salary = 14000;
        employees.Add(emp);

        return employees;
    }