Creating an MD5 hash in C# is straightforward using the built-in cryptography libraries.
✅ Best Practice: Use System.Security.Cryptography.MD5 for string or file hashing.
Example
using System; using System.Security.Cryptography; using System.Text; string ComputeMD5Hash(string input) { using (MD5 md5 = MD5.Create()) { byte[] inputBytes = Encoding.UTF8.GetBytes(input); byte[] hashBytes = md5.ComputeHash(inputBytes); StringBuilder sb = new StringBuilder(); for (int i = 0; i < hashBytes.Length; i++) { sb.Append(hashBytes[i].ToString("x2")); } return sb.ToString(); } }
Why use MD5.Create()? Creates a cryptographic service provider that calculates MD5 hashes efficiently.
For scenarios where you need to hash the contents of a file:
using System; using System.IO; using System.Security.Cryptography; string ComputeFileMD5(string filePath) { using (var md5 = MD5.Create()) using (var stream = File.OpenRead(filePath)) { byte[] hashBytes = md5.ComputeHash(stream); StringBuilder sb = new StringBuilder(); for (int i = 0; i < hashBytes.Length; i++) { sb.Append(hashBytes[i].ToString("x2")); } return sb.ToString(); } }
Why hash files this way? Streams the file content directly through the hash algorithm without loading the entire file into memory.
⚠️ Caution: MD5 is considered cryptographically broken and unsuitable for security purposes. For security-sensitive applications, use SHA-256 or better:
using (SHA256 sha256 = SHA256.Create()) { // Use the same pattern as MD5 examples // Just replace MD5.Create() with SHA256.Create() }
MD5 is still useful for non-security purposes like checksums and data verification.
String interpolation, introduced in C# 6.0, provides a more readable and concise way to format strings compared to traditional concatenation (+) or string.Format(). Instead of manually inserting variables or placeholders, you can use the $ symbol before a string to directly embed expressions inside brackets.
string name = "Walt"; string job = 'Software Engineer'; string message = $"Hello, my name is {name} and I am a {job}"; Console.WriteLine(message);
This would produce the final output of:
Hello, my name is Walt and I am a Software Engineer
String interpolation can also be chained together into a multiline string (@) for even cleaner more concise results:
string name = "Walt"; string html = $@" <div> <h1>Welcome, {name}!</h1> </div>";
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.
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!
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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