This chapter is from the book
This chapter is from the book
This chapter is from the book
Other Commonly Used Types
In addition to the standard predefined types, the .NET Framework provides types for other commonly used values. These types do not have aliases in C# like the predefined types but allow the same operations.
Date and Time
Working with date and time values is done with the DateTime structure, which enables you to create values that represent a date and a time, just a date, or just a time value. The two most common ways to create a new DateTime value are to use one of the various constructor overloads or one of the four static parse methods: Parse, ParseExact, TryParse, or TryParseExact.
The DateTime structure provides several properties; the most common are shown in Table 3.2.
Table 3.2. Common DateTime Properties
Property |
Description |
Date |
Gets the date component of the current instance |
Day |
Gets the day of the month represented by the current instance |
DayOfWeek |
Gets the day of the week represented by the current instance |
Hour |
Gets the hour component of the date represented by the current instance |
Minute |
Gets the minute component of the date represented by the current instance |
Month |
Gets the month component of the date represented by the current instance |
Now |
Gets a DateTime object that is set to the current date and time, in the local time zone |
TimeOfDay |
Gets the time of day for the current instance |
Today |
Gets the current date |
UtcNow |
Gets a DateTime object that is set to the current date and time, in Coordinated Universal Time (UTC) |
Year |
Gets the year component of the date represented by the current instance |
When adding or subtracting date or time values, you can use instance methods, which return a new DateTime value rather than modifying the original one. The common DateTime arithmetic methods are shown in Table 3.3.
Table 3.3. Common DateTime Arithmetic Methods
Method |
Description |
AddDays |
Adds or subtracts the specified number of days |
AddHours |
Adds or subtracts the specified number of hours |
AddMinutes |
Adds or subtracts the specified number of minutes |
AddMonths |
Adds or subtracts the specified number of months |
AddYears |
Adds or subtracts the specified number of years |
It is also possible to subtract two DateTime values using the subtraction operator, which results in a TimeSpan instance. A TimeSpan represents an interval of time measured as a positive or negative number of days, hours, minutes, seconds, and fractions of a second. To ensure consistency, time intervals are measured in days. You can also add a TimeSpan to or subtract a TimeSpan from a DateTime, both of which result in a new DateTime value.
The common methods and properties of TimeSpan are shown in Table 3.4.
Table 3.4. Common TimeSpan Members
Name |
Description |
Add |
Adds the specified TimeSpan to the current instance |
Days |
Gets the days component of the time interval represented by the current TimeSpan |
FromDays |
Returns a TimeSpan that represents a specified number of days |
FromHours |
Returns a TimeSpan that represents a specified number of hours |
FromMilliseconds |
Returns a TimeSpan that represents a specified number of milliseconds |
FromMinutes |
Returns a TimeSpan that represents a specified number of minutes |
FromSeconds |
Returns a TimeSpan that represents a specified number of seconds |
Hours |
Gets the hours component of the time interval represented by the current TimeSpan |
Milliseconds |
Gets the milliseconds component of the time interval represented by the current TimeSpan |
Minutes |
Gets the minutes component of the time interval represented by the current TimeSpan |
Seconds |
Gets the seconds component of the time interval represented by the current TimeSpan |
Subtract |
Subtracts the specified TimeSpan from the current instance |
TotalDays |
Gets the value of the current TimeSpan expressed as whole and fractional days |
TotalHours |
Gets the value of the current TimeSpan expressed as whole and fractional hours |
TotalMilliseconds |
Gets the value of the current TimeSpan expressed as whole and fractional milliseconds |
TotalMinutes |
Gets the value of the current TimeSpan expressed as whole and fractional minutes |
TotalSeconds |
Gets the value of the current TimeSpan expressed as whole and fractional seconds |
Globally Unique Identifiers (GUIDs)
A GUID is a 128-bit integer value that can be used whenever a unique identifier is required that has a low probability of being duplicated. The System.Guid structure enables you to create and compare GUID values. The common members are shown in Table 3.5.
Table 3.5. Common Guid Members
Name |
Description |
CompareTo |
Compares the current instance to the specified Guid |
Empty |
Represents a read-only instance of a Guid whose value is guaranteed to be all zeros |
NewGuid |
Creates a new instance of the Guid structure |
Parse |
Converts the string representation of a GUID into the equivalent Guid instance |
TryParse |
Converts the string representation of a GUID into the equivalent Guid instance, indicating if the conversion was successful |
Uniform Resource Identifiers (URIs)
A uniform resource identifier (URI) is a compact representation of a resource available on the intranet or the Internet and can be an absolute URI (like a web page address) or a relative URI that must be expanded with respect to a base URI.
The Uri class enables you to create new URI values and access the parts of a URI, and provides methods for working with URIs, such as parsing, comparing, and combining. Some of the common members are shown in Table 3.6.
Table 3.6. Common Uri Members
Name |
Description |
AbsoluteUri |
Gets the absolute URI |
Compare |
Compares the specified parts of two Uri instances using the specified comparison rules |
EscapeUriString |
Converts a URI string to its escaped representation |
IsFile |
Gets a value indicating whether the specified Uri is a file URI |
LocalPath |
Gets a local operating-system representation of a filename |
MakeRelativeUri |
Determines the difference between two Uri instances |
TryCreate |
Creates a new Uri but does not throw an exception if the Uri cannot be created |
An instance of the Uri class is immutable. To create a modifiable URI, use the UriBuilder class. The UriBuilder class enables you to easily change the properties of a URI without creating a new instance for each modification. All the properties shown in Table 3.7 are common to both Uri (where they are read-only) and UriBuilder except for the Uri property, which is only available on UriBuilder.
Table 3.7. Common Uri and UriBuilder Properties
Name |
Description |
Fragment |
Gets or sets the fragment portion of the URI |
Host |
Gets or sets the hostname or IP address of a server |
Password |
Gets or sets the password associated with the user who accesses the URI |
Path |
Gets or sets the path to the resource defined by the URI |
Port |
Gets or sets the port number of the URI |
Query |
Gets or sets any query information included in the URI |
Scheme |
Gets or sets the scheme name of the URI |
Uri |
Gets the Uri instance constructed by the specified UriBuilder instance |
UserName |
Gets or sets the username associated with the user who accesses the URI |
Listing 3.1 shows how to use the UriBuilder class.
Listing 3.1. Working with UriBuilder
Uri immutableUri = new Uri("http://www.example.com");
Console.WriteLine(immutableUri);
UriBuilder mutableUri = new UriBuilder(immutableUri);
Console.WriteLine(mutableUri);
mutableUri.Scheme = "https";
mutableUri.Host = "www.example.com";
mutableUri.Path = "exampleFile.html";
Console.WriteLine(mutableUri);
Big Integers and Complex Numbers
The System.Numerics.BigInteger type represents an arbitrarily large integer value that has no theoretical upper or lower bound. When a BigInteger instance has been created, you can use it just as you would any of the other integer types, enabling you to perform basic mathematical operations and comparisons. Listing 3.2 shows some of the ways you can use the BigInteger type.
Listing 3.2. Working with BigInteger
BigInteger b1 = new BigInteger(987321.5401);
BigInteger b2 = (BigInteger)435623411897L;
BigInteger b3 = BigInteger.Parse("435623411897");
Console.WriteLine(BigInteger.Pow(Int32.MaxValue, 2));
Console.WriteLine(b2 == b3);
Console.WriteLine(BigInteger.GreatestCommonDivisor(b1, b2));
The System.Numerics.Complex type represents a complex number, in the form of a + bi, where a is the real part, and b is the imaginary part and allows you to
- Compare two complex numbers to determine equality.
- Perform arithmetic operations, such as addition, subtraction, multiplication, and division; other numerical operations, such as raising a complex number to a specific power; finding the square root or getting the absolute value; and trigonometric operations, such as calculating the cosine of an angle represented by a complex number.
Listing 3.3 shows some of the ways you can use the Complex type.
Listing 3.3. Working with Complex
Complex c1 = new Complex(10, 2); Complex c2 = 3.14; Complex c3 = Complex.FromPolarCoordinates(5, 0.25); Complex c4 = (Complex)10.2m; Console.WriteLine(c1); Console.WriteLine(c2); Console.WriteLine(Complex.Sqrt(c3)); Console.WriteLine(Complex.Exp(c4));