C# — functions

Functions are blocks of code that we can encapsulate for further use. Instead of copying and pasting the same code over and over. We can use a function and reuse it in a more concise and handy way. Here are few examples:

A function can return a value or do some work and return nothing.

The first function returns a double typed number.

static double ReturnNumber(bool condition, double number01, double number02)
{
    double finalNumber = 0;
    if (condition)
    {
        finalNumber = number01 + 15;
    }
    else
    {
        finalNumber = number02 + 25;
    }
    return finalNumber;
}

double returnedNumber = ReturnNumber(false, 5.5, 8.5) + 55;
Console.WriteLine(returnedNumber);

Let’s disassembly the function. The ReturnNumber named function returns a double valued type. There are three input parameters: bool condition, double number01, double number02. A function definition checks the first parameter then assigns a proper value to a finalNumber variable then returns it.

In a program code, outside the function. The function is called and assigned to a returnedNumber double typed variable.

If you don’t want to return any value and make the function to do some work you can use a “void” modifier.

static void ReturnText(int choose, string sentencePart01, string sentencePart02)
{
    string finalSentence;
    switch (choose)
    {
        case 50:
            finalSentence = $"A sentence part 01: {sentencePart01}, Sentence part 02: {sentencePart02}.";
            break;
        case 100:
            finalSentence = $"A sentence part 01: {sentencePart02}, Sentence part 02: {sentencePart02}.";
            break;
        default:
            finalSentence = "Only a sentence.";
            break;
    }
    Console.WriteLine(finalSentence);
}

ReturnText(50, "Part01", "Part02");

The “void” parameter means that the function doesn’t return any value. And an above example indeed does it. When you call it. It concatenates two parameters depending on a condition. Then simply print the variable to a console.

You might wonder whether it is possible to put a function as another function parameter. The answer is yes. It is possible. There are two ways.

Let’s assume we have a list of numbers we want to iterate. Then make a calculation and return a sum of the numbers.

We will create a new function and reuse the previous ReturnNumber function.

List<double> list01 = new List<double>{155.5, 255.6, 355.7};

static double Functions01(Func<bool, double, double, double> function01, List<double> list01)
{
    double value01 = 0;
    foreach (double item in list01)
    {
        value01 = value01 + function01(true, item, 2.5); 
    }
    return value01; 
}

Console.WriteLine(Functions01(ReturnNumber, list01));

The ReturnNumber function is the first parameter of the Functions01 function. Func<bool, double, double, double> means that the ReturnNumber function input is bool, double, double and returns a double type (the last one).

There is a second way to do the same stuff. We can use delegates.

public delegate double FunctionDelegate(bool c, double n01, double n02);

List<double> list01 = new List<double>{155.5, 255.6, 355.7};

static double Functions02(FunctionDelegate function02, List<double> list01)
{
    double value01 = 0;
    foreach (double item in list01)
    {
        value01 = value01 + function02(true, item, 2.5); 
    }
    return value01; 
}

Console.WriteLine(Functions02(ReturnNumber, list01));

Firstly, we create a delegate named FunctionDelegate. Then place the delegate as a parameter of the function.

Here is an output of four previous functions:

Now, we create a real-world example. In this post, we’ve been calling an MS Fabric REST API from a C# code: C# and Power BI REST API

In order to create an authentication token and obtain an Http client we placed the code inside an application. This is a good candidate to put it in a function and reuse depending on our needs.

static HttpClient AzureCredentialFabric(bool readMode, string tenantId, string clientId, string secret)
{
    string token;

    if (readMode) // Type of a credential we want to use
    {
        var credential = new ClientSecretCredential(tenantId, clientId, secret); // A service principal
        token = credential.GetToken(new Azure.Core.TokenRequestContext(new[] { "https://analysis.windows.net/powerbi/api/.default" })).Token.ToString();
    }
    else
    { // Authenticate first: az login --scope https://graph.microsoft.com/.default --allow-no-subscriptions or use an Azure credential
        var credential = new ChainedTokenCredential(new AzureCliCredential(), new DefaultAzureCredential());
        token = credential.GetToken(new Azure.Core.TokenRequestContext(new[] { "https://analysis.windows.net/powerbi/api/.default" })).Token.ToString();
    }

    // An http client with enriched witch a Bearer token.
    HttpClient client = new HttpClient();
    client.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", token);
    return client;

}

HttpClient client = AzureCredentialFabric(true, "3*****7", "e*****4", "Z*****J");

// A call to an MS Fabric REST API
var workspacesResponse = client.GetStringAsync("https://api.powerbi.com/v1.0/myorg/groups");
Console.WriteLine(workspacesResponse.Result);

And here is the code on GitHub.

If you want to look how to work with object then feel more than welcome in here: C# — objects. C# is an object oriented programming… | by Michal Molka | Nov, 2024 | Medium