Namespaces and using directives in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of accessing classes with namespaces

What is the output of this C# program?

C Sharp (C#)

namespace Alpha {
    public class Printer {
        public static string Print() => "Alpha Printer";
    }
}

namespace Beta {
    public class Printer {
        public static string Print() => "Beta Printer";
    }
}

class Program {
    static void Main() {
        System.Console.WriteLine(Alpha.Printer.Print());
        System.Console.WriteLine(Beta.Printer.Print());
    }
}

A Compilation error due to ambiguous Printer class

B Beta Printer\nAlpha Printer

C Alpha Printer

D Alpha Printer\nBeta Printer

💡 Hint

Look at how fully qualified names are used to call Print methods.

The program calls Print() from Alpha.Printer and Beta.Printer explicitly, so it prints both lines in order.

❓ Predict Output

intermediate

Effect of using directive on ambiguous class names

Given these namespaces and using directives, what will be the output?

C Sharp (C#)

using Alpha;
using Beta;

namespace Alpha {
    public class Printer {
        public static string Print() => "Alpha Printer";
    }
}

namespace Beta {
    public class Printer {
        public static string Print() => "Beta Printer";
    }
}

class Program {
    static void Main() {
        System.Console.WriteLine(Printer.Print());
    }
}

A Compilation error due to ambiguous Printer

B Beta Printer

C Alpha Printer

D Runtime error

💡 Hint

Two namespaces contain Printer class, both imported with using.

The compiler cannot decide which Printer to use because both Alpha and Beta namespaces are imported and both have Printer class. This causes a compilation error.

❓ Predict Output

advanced

Using alias directive to resolve ambiguity

What is the output of this program using alias directives?

C Sharp (C#)

using A = Alpha.Printer;
using B = Beta.Printer;

namespace Alpha {
    public class Printer {
        public static string Print() => "Alpha Printer";
    }
}

namespace Beta {
    public class Printer {
        public static string Print() => "Beta Printer";
    }
}

class Program {
    static void Main() {
        System.Console.WriteLine(A.Print());
        System.Console.WriteLine(B.Print());
    }
}

A Runtime error

B Beta Printer\nAlpha Printer

C Alpha Printer\nBeta Printer

D Compilation error due to alias misuse

💡 Hint

Alias directives create shortcuts to fully qualified names.

Alias directives A and B refer to Alpha.Printer and Beta.Printer respectively, so calling A.Print() and B.Print() prints both lines correctly.

❓ Predict Output

advanced

Namespace nesting and class access

What will this program print?

C Sharp (C#)

namespace Outer {
    public class Printer {
        public static string Print() => "Outer Printer";
    }
    namespace Inner {
        public class Printer {
            public static string Print() => "Inner Printer";
        }
    }
}

class Program {
    static void Main() {
        System.Console.WriteLine(Outer.Printer.Print());
        System.Console.WriteLine(Outer.Inner.Printer.Print());
    }
}

A Inner Printer\nOuter Printer

B Outer Printer\nInner Printer

C Compilation error due to nested namespace

D Runtime error

💡 Hint

Nested namespaces are accessed by chaining names.

Outer.Printer.Print() calls the class in Outer namespace, Outer.Inner.Printer.Print() calls the nested Inner namespace class. Both print their respective strings.

❓ Predict Output

expert

Using directives and static class members

What is the output of this program?

C Sharp (C#)

using static System.Math;

class Program {
    static void Main() {
        double x = 3.0;
        double y = Sqrt(x * x);
        System.Console.WriteLine(y);
    }
}

A 3

B 9

C Compilation error due to using static

D Runtime error

💡 Hint

using static allows calling static members without class name.

Sqrt is called directly because of using static System.Math; Sqrt(3*3) = 3, so output is 3.