I code therefore I am.

Hex String to Color (ARGB)

public Color HexStringToColor(string hex)
{
	hex = hex.Replace("#", "").ToLowerInvariant();

	
	if (hex.Length == 6)
	{
		hex = "ff" + hex;
	}
	else if (hex.Length != 8)
	{
		throw new Exception(hex + " 
			is not a valid 6 or 8-place 
			hexadecimal color code.");
	}

	int a, r, g, b;
	a = Convert.ToInt32(hex.Substring(0, 2), 16);
	r = Convert.ToInt32(hex.Substring(2, 2), 16);
	g = Convert.ToInt32(hex.Substring(4, 2), 16);
	b = Convert.ToInt32(hex.Substring(6, 2), 16);

	return Color.FromArgb(a, r, g, b);
}

NSDate to DateTime and Back

• Reference Date is January 1, 2001 0:00:00 UTC (GMT)
• It’s important to note the Local Time Zone vs. UTC/GMT

public static DateTime NSDateToDateTime(NSDate date)
{
    DateTime reference = TimeZone.CurrentTimeZone.ToLocalTime( 
        new DateTime(2001, 1, 1, 0, 0, 0) );
    return reference.AddSeconds(date.SecondsSinceReferenceDate);
}

public static NSDate DateTimeToNSDate(DateTime date)
{
    DateTime reference = TimeZone.CurrentTimeZone.ToLocalTime(
        new DateTime(2001, 1, 1, 0, 0, 0) );
    return NSDate.FromTimeIntervalSinceReferenceDate(
        (date - reference).TotalSeconds);
}

Integer to Ordinal

public string AddOrdinal(int num)
{
    switch(num % 100)
    {
        case 11:
        case 12:
        case 13:
            return num.ToString() + "th";
    }

    switch(num % 10)
    {
        case 1:
            return num.ToString() + "st";
        case 2:
            return num.ToString() + "nd";
        case 3:
            return num.ToString() + "rd";
        default:
            return num.ToString() + "th";
    }
}

age from birthday

Rather than dividing figures by a fixed number days (which ignores special cases like leap years), I find this method quite reliable.

//Given DateTime birthday
TimeSpan span = DateTime.Now - birthday;
DateTime time = DateTime.MinValue + span;
int age = time.Year - 1; 

System.IO.Path.Combine Behavior

When using Path.Combine, you should be aware of the behavior that if the second parameter has a leading slash, it will ignore the first parameter.

Given the following:

string root = "c:\";
string path = "test.txt";
string lead = "\test.txt";

We get the following results:

using System.IO;
…
Path.Combine(root, path); // ‘c:\test.txt’
Path.combine(root, lead); // ‘\test.txt’

Safe Casting

Use the as keyword.

MyClass castedObject = obj as MyClass;

This won’t throw a class cast exception. Instead, castedObject will return null if obj isn’t a MyClass.

Chain ?? Operators

You can use multiple ?? operators to chain multiple null comparisons:

string text = value1 ?? value2 ?? String.Empty;

Normalizing & Comparing Strings

When normalizing strings, it is highly recommended that you use ToUpperInvariant instead of ToLowerInvariant because Microsoft has optimized the code for performing uppercase comparisons.

[source: CLR via C# ]