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C#: .NET: Number
Decimal-type

Decimal accurately stores numeric data. The .NET Framework offers this type for programs where rounding errors are harmful. Decimal stores large and small numbers with many digits after the decimal place.


Operators. The decimal type is a value type. It can be manipulated with the standard numeric operators in the C# language. These include the plus, minus, multiply and divide operators. Decimal also has other features, as we see later.

Also: You can test decimal values with the equality operator == and print decimals to the Console.

Console
C# program that uses decimal operators

using System;

class Program
{
    static void Main()
    {
	decimal d = 1.0M;
	// Test decimal.
	if (d == 1.0M)
	{
	    Console.WriteLine(d);
	}
	decimal y = 0.5M;
	// Add decimal.
	y += d;
	Console.WriteLine(y);
	// Subtract and multiply decimal.
	y -= (d * 2);
	Console.WriteLine(y);
    }
}

Output

1.0
1.5
-0.5

One: 1

Constants. If you want to know the maximum or minimum value of the decimal type, there is no need to look this up or memorize it. You instead should access the MaxValue and MinValue constants.

Also: You can use the One, Zero, and MinusOne constants. Using these constants may provide for more self-documenting code.

C# program that reveals decimal constants

using System;

class Program
{
    static void Main()
    {
	Console.WriteLine(decimal.MaxValue);
	Console.WriteLine(decimal.MinValue);
	Console.WriteLine(decimal.One);
	Console.WriteLine(decimal.Zero);
	Console.WriteLine(decimal.MinusOne);
    }
}

Output

79228162514264337593543950335
-79228162514264337593543950335
1
0
-1

Floor numeric function

Floor, Ceiling. When using decimal, you should call methods available on the decimal class instead of those in the Math class for accuracy reasons. When you take the ceiling of 1.1, you get 2. When you take the floor of that same number, you receive 1.

Math.CeilingMath.Floor

So: Ceiling is the integer above the number and the floor is the integer below the number.

C# program that uses Ceiling and Floor methods

using System;

class Program
{
    static void Main()
    {
	Console.WriteLine(decimal.Ceiling(1.1M));
	Console.WriteLine(decimal.Floor(1.1M));
    }
}

Output

2
1

Programming tip

Arithmetic. To improve the clarity of decimal manipulations, you can use the Add, Multiply, Subtract and Divide methods. Each of these methods receives two arguments. You can imagine the classic arithmetic operator in between the two arguments.

C# program that uses math methods

using System;

class Program
{
    static void Main()
    {
	Console.WriteLine(decimal.Add(1.1M, 1.3M)); // Add
	Console.WriteLine(decimal.Multiply(5.0M, 2.0M)); // Five times two
	Console.WriteLine(decimal.Subtract(2.0M, 1.0M)); // Two minus one
	Console.WriteLine(decimal.Divide(10M, 2M)); // Ten divided by two
    }
}

Output

2.4
10.00
1.0
5

Remainder. When doing important computations with money, you may want to get the remainder of a division. The remainder is the part left over after the division completes. In this program, we show that the remainder of 2 divided by 1.5 is 0.5.

Tip: This is because the 0.5 is left over after the division occurred. This is called the remainder.

C# program that uses Remainder method

using System;

class Program
{
    static void Main()
    {
	// Remainder of 2 divided by 1.5 is 0.5
	Console.WriteLine(decimal.Remainder(2.0M, 1.5M));
    }
}

Output

0.5

Truncate. Another useful method you can invoke on the decimal type is the Truncate method. This method simply erases all the numbers after the decimal place. It doesn't take into consideration whether the number would be rounded up or rounded down.

This program shows that when we truncate 4.55, we get the number 4. Truncate returns a value of type decimal. It is similar to casting down, as with (int), but has different behavior on values that cannot be represented with int.

Int TypeCast to Int
C# program that uses Truncate method

using System;

class Program
{
    static void Main()
    {
	// Truncate removes the digits after the decimal place.
	Console.WriteLine(decimal.Truncate(4.55M));
    }
}

Output

4

Negate makes positive decimals negative, and makes negative decimals positive. You could duplicate this functionality by multiplying by negative one, but this method is more self-documenting.

C# that uses Negate method

using System;

class Program
{
    static void Main()
    {
	// Makes positive numbers negative, and negative numbers positive.
	Console.WriteLine(decimal.Negate(1.5M));
	Console.WriteLine(decimal.Negate(-1.5M));
    }
}

Output

-1.5
1.5

Math written on chalkboard

Round, MidpointRounding. The Round method on the decimal type is useful for many programs. The decimal.Round method by default rounds down or up to the specified decimal place. You can specify the MidpointRounding to further define the required behavior.

Note: The ToEven value means that when a number needs to be rounded, it is always rounded to the nearest even number.

Note 2: The AwayFromZero value means that numbers are rounded up for positive numbers and down for negative numbers.

C# that uses decimal.Round method

using System;

class Program
{
    static void Main()
    {
	// Round to one decimal place.
	Console.WriteLine(decimal.Round(1.59M, 1));

	// Demonstrate MidpointRounding enumeration.
	Console.WriteLine(decimal.Round(2.5M, 0, MidpointRounding.ToEven));
	Console.WriteLine(decimal.Round(2.5M, 0, MidpointRounding.AwayFromZero));
    }
}

Output

1.6
2
3

String-type

Parse, TryParse. The decimal type lets you convert from strings to actual decimals. The decimal.Parse method will throw an exception if you feed it an incorrectly-formatted value. The decimal.TryParse method will handle errors by returning a false value.

Tip: You should use Parse if you expect all input will be correct, and TryParse if you expect errors to be common.

C# that parses strings into decimals

using System;

class Program
{
    static void Main()
    {
	// Use Parse on arguments that are always correct.
	decimal value = decimal.Parse("100.01");
	Console.WriteLine(value);

	// Use TryParse when errors are expected.
	decimal value2;
	if (decimal.TryParse("perl", out value2))
	{
	    Console.WriteLine("Not reached");
	}
    }
}

Output

100.01

Convert or change

Convert. Because the decimal type is 16 bytes, it is wasteful to store many decimals when you do not need that much accuracy. You can use the To* methods on the decimal type to convert to smaller memory representations of the number.

Caution: Exceptions occur if the conversion cannot be done because the decimal value is too large to be represented in the target type.

C# that converts from decimal type

using System;

class Program
{
    static void Main()
    {
	const decimal input = 5;
	// Convert this decimal into other compatible types.
	Console.WriteLine(decimal.ToByte(input));
	Console.WriteLine(decimal.ToDouble(input));
	Console.WriteLine(decimal.ToInt16(input));
	Console.WriteLine(decimal.ToInt32(input));
	Console.WriteLine(decimal.ToInt64(input));
	Console.WriteLine(decimal.ToSByte(input));
	Console.WriteLine(decimal.ToSingle(input));
	Console.WriteLine(decimal.ToUInt16(input));
	Console.WriteLine(decimal.ToUInt32(input));
	Console.WriteLine(decimal.ToUInt64(input));
    }
}

Output

5
5
5
5
5
5
5
5
5
5

Programming tip

FromOACurrency, ToOACurrency. The Decimal type provides FromOACurrency and ToOACurrency. FromOACurrency receives an OA value and converts it into a decimal. ToOACurrency takes a decimal and converts it into an OA value. OA values are a Microsoft-specific encoding.

Note: You should only use these methods if you are translating Excel spreadsheets or certain Microsoft database formats.

FromOADate and Excel Dates
Garbage collection visualization

Memory. How much memory does the decimal type use? As stated in this article, it requires 16 bytes. This site also contains a more detailed examination of the memory usage of the decimal type.

Decimal Memory
Framework: NET

Summary. The decimal type is a powerful and accurate representation for number data in memory. With its large selection of static methods, the decimal type is valuable for representing important quantities like amounts of money.

Numbers