How to Use Reflection in C# to Dynamically Invoke Methods

Reflection in C# allows you to inspect and interact with types dynamically at runtime. It is useful for scenarios like plugin systems, dependency injection, and working with unknown assemblies.

Getting Started with Reflection

To use reflection, include the System.Reflection namespace:

using System;
using System.Reflection;

Invoking a Method Dynamically

You can use reflection to call methods on an object when you don't know the method name at compile time.

class Sample
{
    public void SayHello() => Console.WriteLine("Hello from Reflection!");
}

var sample = new Sample();
MethodInfo method = typeof(Sample).GetMethod("SayHello");
method?.Invoke(sample, null);
// Output: Hello from Reflection!

Invoking Methods with Parameters

If a method requires parameters, pass them as an object array:

class MathOperations
{
    public int Add(int a, int b) => a + b;
}

var math = new MathOperations();
MethodInfo method = typeof(MathOperations).GetMethod("Add");
object result = method?.Invoke(math, new object[] { 5, 3 });
Console.WriteLine(result); // Output: 8

Working with Static Methods

For static methods, pass null as the target object:

class Utility
{
    public static string GetMessage() => "Static method called!";
}

MethodInfo method = typeof(Utility).GetMethod("GetMessage");
object result = method?.Invoke(null, null);
Console.WriteLine(result); // Output: Static method called!

Performance Considerations

  • Reflection is slower than direct method calls because it bypasses compile-time optimizations.
  • Use Delegate.CreateDelegate to improve performance when invoking frequently:
Func<int, int, int> add = (Func<int, int, int>)Delegate.CreateDelegate(
    typeof(Func<int, int, int>),
    typeof(MathOperations).GetMethod("Add")
);
Console.WriteLine(add(5, 3)); // Output: 8

Conclusion

Reflection in C# is a powerful tool for dynamic method invocation. While it introduces some performance overhead, it is invaluable in scenarios requiring runtime flexibility, such as plugins, serialization, and dynamic dependency loading.

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Related

Reading a file line by line is useful when handling large files without loading everything into memory at once.

✅ Best Practice: Use File.ReadLines() which is more memory efficient.

Example

foreach (string line in File.ReadLines("file.txt"))
{
    Console.WriteLine(line);
}

Why use ReadLines()?

Reads one line at a time, reducing overall memory usage. Ideal for large files (e.g., logs, CSVs).

Alternative: Use StreamReader (More Control)

For scenarios where you need custom processing while reading the contents of the file:

using (StreamReader reader = new StreamReader("file.txt"))
{
    string? line;
    while ((line = reader.ReadLine()) != null)
    {
        Console.WriteLine(line);
    }
}

Why use StreamReader?

Lets you handle exceptions, encoding, and buffering. Supports custom processing (e.g., search for a keyword while reading).

When to Use ReadAllLines()? If you need all lines at once, use:

string[] lines = File.ReadAllLines("file.txt");

Caution: Loads the entire file into memory—avoid for large files!

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Storing passwords as plain text is dangerous. Instead, you should hash them using a strong, slow hashing algorithm like BCrypt, which includes built-in salting and resistance to brute-force attacks.

Step 1: Install BCrypt NuGet Package

Before using BCrypt, install the BCrypt.Net-Next package:

dotnet add package BCrypt.Net-Next

or via NuGet Package Manager:

Install-Package BCrypt.Net-Next

Step 2: Hash a Password

Use BCrypt.HashPassword() to securely hash a password before storing it:

using BCrypt.Net;

string password = "mySecurePassword123";
string hashedPassword = BCrypt.HashPassword(password);

Console.WriteLine(hashedPassword); // Output: $2a$12$...

Step 3: Verify a Password

To check a user's login attempt, use BCrypt.Verify():

bool isMatch = BCrypt.Verify("mySecurePassword123", hashedPassword);
Console.WriteLine(isMatch); // Output: True

Ensuring proper hashing should be at the top of your list when it comes to building authentication systems.

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When working with URLs in C#, encoding is essential to ensure that special characters (like spaces, ?, &, and =) don’t break the URL structure. The recommended way to encode a string for a URL is by using Uri.EscapeDataString(), which converts unsafe characters into their percent-encoded equivalents.

string rawText = "hello world!";
string encodedText = Uri.EscapeDataString(rawText);

Console.WriteLine(encodedText); // Output: hello%20world%21

This method encodes spaces as %20, making it ideal for query parameters.

For ASP.NET applications, you can also use HttpUtility.UrlEncode() (from System.Web), which encodes spaces as +:

using System.Web;

string encodedText = HttpUtility.UrlEncode("hello world!");
Console.WriteLine(encodedText); // Output: hello+world%21

For .NET Core and later, Uri.EscapeDataString() is the preferred choice.

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