C# Switch Case with 💻Lamda Expression

In C#, the switch statement is used for conditional branching based on the value of an expression. It allows you to compare the expression against multiple possible constant values (cases) and execute the code block associated with the first matching case. The switch statement provides a more concise way to handle multiple conditional branches compared to using a series of if-else if statements.

C# Switch Case with Lamda Expression

Switch Case: Before Using Lambda Expressions

public static class WithoutLambdaExpressions
    {
        public static string GetLetterGrade(int numericalGrade)
        {
            string letterGrade;

            switch (numericalGrade)
            {
                case int n when n >= 90:
                    letterGrade = "A";
                    break;
                case int n when n >= 80:
                    letterGrade = "B";
                    break;
                case int n when n >= 70:
                    letterGrade = "C";
                    break;
                case int n when n >= 60:
                    letterGrade = "D";
                    break;
                default:
                    letterGrade = "F";
                    break;
            }

            return letterGrade;
        }
    }

In this example:

1. The program prompts the user to enter a numerical grade.
2. It uses int.TryParse to convert the user's input into an integer.
3. The GetLetterGrade function takes the numerical grade as an argument and uses a switch statement to determine the corresponding letter grade.
4. The switch statement uses pattern matching (case int n when n >= 90) to specify conditions for each case.
5. The resulting letter grade is then displayed to the user.

This example demonstrates how to use a switch statement to perform conditional branching based on the value of a variable.

Switch Case: After Using Lambda Expressions

public static class UsingLambdaExpressions
    {
        public static Func<int, string> GetLetterGrade = grade => new Dictionary<int, string>
        {
            { 90, "A" },
            { 80, "B" },
            { 70, "C" },
            { 60, "D" }
        }.FirstOrDefault(entry => grade >= entry.Key).Value ?? "F";
    }

In this code:

1. We define a dictionary that maps numerical grades to letter grades.
2. We use the FirstOrDefault method with a lambda expression to find the first entry in the dictionary where the numerical grade is greater than or equal to the key.
3. If no matching entry is found, it defaults to “F”.
4. We define GetLetterGrade as a lambda expression that takes an integer argument and returns the corresponding letter grade using the dictionary and FirstOrDefault.

This lambda expression achieves the same result as the original GetLetterGrade method but in a more compact way using a dictionary and LINQ.

Execute Program

using SwitchCaseExm;


Console.Write("Enter your numerical grade: ");
if (int.TryParse(Console.ReadLine(), out int numericalGrade))
{
    string _WithoutLambdaExpressions = WithoutLambdaExpressions.GetLetterGrade(numericalGrade);
    string _UsingLambdaExpressions = UsingLambdaExpressions.GetLetterGrade(numericalGrade);
    Console.WriteLine($"Your letter grade is: {_UsingLambdaExpressions}");
}
else
{
    Console.WriteLine("Invalid input. Please enter a numerical grade.");
}

Output

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