Decoding T-SQL CAST in C#/VB.NET

sql

encoding

t-sql

csharp

byAlex Kataev·Aug 27, 2024

To interpret a T-SQL CAST in C# or VB.NET, leverage .NET type conversion methods. Invoke Convert.To<Type>() and you're all set. Here's what our boilerplate looks like:

// Well, aren't you a number! String to int
int num = Convert.ToInt32("123");

// Listen mate, it's a date! String to DateTime
DateTime date = Convert.ToDateTime("2023-01-01");

// Hex me up! Byte array to Base64 string
string base64 = Convert.ToBase64String(new byte[] { 0x0, 0x1, 0x2 });

For VB.NET, the magic lies within the same realm of Convert methods:

' Oh, so now you're a number? String to int
Dim num As Integer = Convert.ToInt32("123")

' Date or date not, there is no try! String to DateTime
Dim date As DateTime = Convert.ToDateTime("2023-01-01")

' Hex to the max! Byte array to Base64 string
Dim base64 As String = Convert.ToBase64String(New Byte() {0, 1, 2})

In the land of C# and VB.NET, *Convert class methods are your passport to **amate T-SQL CAST.

Beyond basic conversions: ASCII magic and pitfalls

Alright, let's say T-SQL handed you a hex-encoded string representing ASCII characters. You now hold the secret recipe for transforming this hex jumble into human-readable text by dissecting each hex pair, and converting them into characters.

string encodedString = "48656C6C6F";  // "Hello" in disguise
StringBuilder decodedBuilder = new StringBuilder();
for (int i = 0; i < encodedString.Length; i += 2)
{
    string hexPair = encodedString.Substring(i, 2); // Pairs? We talkin' about pairs?
    int asciiCode = Int32.Parse(hexPair, System.Globalization.NumberStyles.HexNumber);
    char character = Convert.ToChar(asciiCode);
    decodedBuilder.Append(character);
    // Knock, Knock. Who’s there? ASCII.
}
string decodedString = decodedBuilder.ToString(); // "Hello" in clear sight

The same operation can be made in VB.NET by using Mid and ChrW:

Dim encodedString As String = "48656C6C6F" ' "Hello", but hex
Dim decodedBuilder As New StringBuilder()
Dim character As Char
For i = 1 To Len(encodedString) Step 2
    Dim hexPair As String = Mid(encodedString, i, 2)
    Dim asciiCode As Integer = Int32.Parse(hexPair, Globalization.NumberStyles.HexNumber)
    character = ChrW(asciiCode)
    decodedBuilder.Append(character)
    ' ASCII-whosy? You're in Hex-town now!
Next
Dim decodedString As String = decodedBuilder.ToString() ' "Hello", but normal

Getting a grip on common hurdles

Ensure correct format: Objects in mirror are closer than they appear. Same applies to string formatting when converting. Confirm that strings are formatted correctly and do not include prefixes like 0x.
Two-byte Unicode: Remember that each Unicode character uses two bytes. Align yourself correctly with the byte pairing.
Experiment actively: When the going gets tough, the tough get going. If one method fails, do not retreat. Fight through with URL decoding, ASCII/Unicode encoding, or byte parsing techniques.

Strategies for decoding complex cases

If you encounter more complex encodings, such as those including Unicode characters, make sure to understand the specifics and adopt a strategy to decode them.

Decoding extended ASCII or Unicode

Encoded strings may involve characters outside the ASCII range. You can leverage .NET's character encoding framework to handle these cases:

string unicodeEncodedString = "00E4006F0072006E";
byte[] bytes = Enumerable.Range(0, unicodeEncodedString.Length)
                         .Where(x => x % 2 == 0)
                         .Select(x => Convert.ToByte(unicodeEncodedString.Substring(x, 2), 16))
                         .ToArray();
string result = Encoding.Unicode.GetString(bytes); // "èorn"

For VB.NET, be sure to adjust the loop accordingly:

Dim unicodeEncodedString As String = "00E4006F0072006E"
Dim bytes() As Byte = Enumerable.Range(0, unicodeEncodedString.Length) _
                                .Where(Function(x) x Mod 2 = 0) _
                                .Select(Function(x) Convert.ToByte(unicodeEncodedString.Substring(x, 2), 16)) _
                                .ToArray()
Dim result As String = Text.Encoding.Unicode.GetString(bytes) ' "èorn"

Offering your solutions

Alright, champ! You've nailed it. Don't forget to share your solutions on open-source platforms like GitHub. This allows others to utilize and refine them. Elevate your squad's game. Share the knowledge!

Troubleshooting common encoding issues

Encoding can get trippy rapidly. Here are some points that could save your day:

Incorrect byte ordering: You don't put your socks on after your shoes, do you? Ensure your byte ordering (Big Endian or Little Endian) aligns with the original encoding.
Improper encoding selection: Make sure you match the correct .NET Encoding object to the actual charset used in the original encoding.
Inconsistent input validation: Do check the validity of input strings. Coding is fun, null reference exceptions and format errors are not.