{"id":304,"date":"2022-01-03T18:31:23","date_gmt":"2022-01-03T11:31:23","guid":{"rendered":"https:\/\/csharptutorial.net\/?page_id=304"},"modified":"2022-06-03T13:41:53","modified_gmt":"2022-06-03T06:41:53","slug":"csharp-property","status":"publish","type":"page","link":"https:\/\/www.csharptutorial.net\/csharp-tutorial\/csharp-property\/","title":{"rendered":"C# Property"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll about the C# property and how to use the properties effectively.<\/p>\n\n\n\n

Introduction to the C# property<\/h2>\n\n\n\n

By definition, a property is a member of a class<\/a> that provides a flexible way to read, write, or compute the value of a private field.<\/p>\n\n\n\n

For example, the following defines the class Person<\/code> with three private fields firstName<\/code>, lastName<\/code>, and age<\/code>:<\/p>\n\n\n

\/\/ Person.cs<\/span>\n\nclass<\/span> Person<\/span>\n{\n    private<\/span> string<\/span> firstName;\n    private<\/span> string<\/span> lastName;\n    private<\/span> int<\/span> age;   \n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
To assign values to and read values from these private fields, you use properties. The following shows how to add three properties to the Person<\/code> class:<\/p>\n\n\n
\/\/ Person.cs<\/span>\n\nclass<\/span> Person<\/span>\n{\n    private<\/span> string<\/span> firstName;\n    private<\/span> string<\/span> lastName;\n    private<\/span> int<\/span> age;\n\n\n    public<\/span> string<\/span> FirstName\n    {\n        get<\/span> { return<\/span> firstName; }\n        set<\/span> { firstName = value<\/span>; }\n    }\n\n    public<\/span> string<\/span> LastName\n    {\n        get<\/span> { return<\/span> lastName; }\n        set<\/span> { lastName = value<\/span>; }\n    }\n\n    public<\/span> int<\/span> Age\n    {\n        get<\/span> { return<\/span> age; } \n        set<\/span> { age = value<\/span>; }\n    }\n\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
In this example, we declare a property like a field with a get<\/code> and set<\/code> blocks. The get<\/code> and set<\/code> are called the property accessors.<\/p>\n\n\n\n
When you read from a property, the get<\/code> accessor executes. And when you assign a value to a property, the set<\/code> accessor executes. For example:<\/p>\n\n\n
\/\/ Program.cs<\/span>\n\nvar<\/span> p1 = new<\/span> Person();\n\np1.FirstName = \"John\"<\/span>;\np1.LastName  = \"Doe\"<\/span>;\n\nConsole.WriteLine($\"{p1.FirstName}<\/span> {p1.LastName}<\/span>\"<\/span>);<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
In this example:<\/p>\n\n\n\n
  • First, create an instance of the Person<\/code> class.<\/li>
  • Second, assign the values to the FirstName<\/code> and LastName<\/code> properties.<\/li>
  • Third, read values from the FirstName<\/code> and LastName<\/code> properties.<\/li><\/ul>\n\n\n\n
    Using C# property for data validation<\/h2>\n\n\n\n
    Since a property provides a central place to assign a value to a private field, you can validate the data and throw an exception if the data is not valid.<\/p>\n\n\n\n
    Suppose you want to implement the following validation rules: <\/p>\n\n\n\n
    • The first name and last name are not null or empty<\/li>
    • The age is between 1 and 150<\/li><\/ul>\n\n\n\n
      To do that, you can add the validation logic to the set<\/code> accessors of the properties as shown in the following example:<\/p>\n\n\n
      \/\/ Person.cs<\/span>\n\nclass<\/span> Person<\/span>\n{\n    private<\/span> string<\/span> firstName;\n    private<\/span> string<\/span> lastName;\n    private<\/span> int<\/span> age;\n\n    public<\/span> string<\/span> FirstName\n    {\n        get<\/span>\n        {\n            return<\/span> firstName;\n        }\n        set<\/span>\n        {\n            if<\/span> (string<\/span>.IsNullOrEmpty(value<\/span>))\n            {\n                throw<\/span> new<\/span> ArgumentException(\"The first name must not be empty or null\"<\/span>);\n            }\n\n            firstName = value<\/span>;\n        }\n    }\n\n    public<\/span> string<\/span> LastName\n    {\n        get<\/span>\n        {\n            return<\/span> lastName;\n        }\n        set<\/span>\n        {\n            if<\/span> (string<\/span>.IsNullOrEmpty(value<\/span>))\n            {\n                throw<\/span> new<\/span> ArgumentException(\"The last name must not be empty or null\"<\/span>);\n            }\n\n            lastName = value<\/span>;\n        }\n    }\n\n    public<\/span> int<\/span> Age\n    {\n        get<\/span>\n        {\n            return<\/span> age;\n        }\n        set<\/span>\n        {\n            if<\/span> (value<\/span> < 0<\/span> || value<\/span> > 150<\/span>)\n            {\n                throw<\/span> new<\/span> ArgumentException(\"The age must be between 1 and 150\"<\/span>);\n            }\n\n            age = value<\/span>;\n        }\n    }\n\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
      The following program causes an exception because the age is out of the valid range (1-150)<\/p>\n\n\n
      \/\/ Program.cs<\/span>\n\nvar<\/span> p1 = new<\/span> Person();\n\np1.FirstName = \"John\"<\/span>;\np1.LastName  = \"Doe\"<\/span>;\np1.Age = 200<\/span>; \/\/ cause an exception<\/span><\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
      Output:<\/p>\n\n\n
      Unhandled exception. System.ArgumentException: The age must be between 1<\/span> and 150<\/span><\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
      C# computed property<\/h2>\n\n\n\n
      To create a computed property, you can implement the get<\/code> accessor. For example, you can create a FullName<\/code> property that returns the concatenation of the first name and last name:<\/p>\n\n\n
      \/\/ Person.cs<\/span>\n\nclass<\/span> Person<\/span>\n{\n    private<\/span> string<\/span> firstName;\n    private<\/span> string<\/span> lastName;\n    private<\/span> int<\/span> age;\n\n    public<\/span> string<\/span> FirstName\n    {\n        get<\/span>\n        {\n            return<\/span> firstName;\n        }\n        set<\/span>\n        {\n            if<\/span> (string<\/span>.IsNullOrEmpty(value<\/span>))\n            {\n                throw<\/span> new<\/span> ArgumentException(\"The first name must not be empty or null\"<\/span>);\n            }\n\n            firstName = value<\/span>;\n\n\n        }\n    }\n\n    public<\/span> string<\/span> LastName\n    {\n        get<\/span>\n        {\n            return<\/span> lastName;\n        }\n        set<\/span>\n        {\n            if<\/span> (string<\/span>.IsNullOrEmpty(value<\/span>))\n            {\n                throw<\/span> new<\/span> ArgumentException(\"The last name must not be empty or null\"<\/span>);\n            }\n\n            lastName = value<\/span>;\n        }\n    }\n\n    public<\/span> int<\/span> Age\n    {\n        get<\/span>\n        {\n            return<\/span> age;\n        }\n        set<\/span>\n        {\n            if<\/span> (value<\/span> < 0<\/span> || value<\/span> > 150<\/span>)\n            {\n                throw<\/span> new<\/span> ArgumentException(\"The age must be between 1 and 150\"<\/span>);\n            }\n\n            age = value<\/span>;\n        }\n    }\n\n    public<\/span> string<\/span> FullName\n    {\n        get<\/span> \n        {\n            return<\/span> $\"{FirstName}<\/span> {LastName}<\/span>\"<\/span>;\n        }\n    }\n\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
      And you can read from the FullName<\/code> property:<\/p>\n\n\n
      \/\/ Program.cs<\/span>\n\nvar<\/span> p1 = new<\/span> Person();\n\np1.FirstName = \"Jane\"<\/span>;\np1.LastName  = \"Doe\"<\/span>;\np1.Age = 25<\/span>;\n\nConsole.WriteLine(p1.FullName);<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
      Output:<\/p>\n\n\n
      Jane Doe<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
      If you attempt to assign a value to the FullName<\/code> property, you’ll get a compilation error. For example:<\/p>\n\n\n
      \/\/ Program.cs<\/span>\n\nvar<\/span> p1 = new<\/span> Person();\n\np1.FirstName = \"Jane\"<\/span>;\np1.LastName  = \"Doe\"<\/span>;\np1.Age = 25<\/span>;\n\nConsole.WriteLine(p1.FullName);\n\np1.FullName = \"Jane Smith\"<\/span>;<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
      Error:<\/p>\n\n\n
      Property or indexer 'Person.FullName'<\/span> cannot be assigned to -- it is<\/span> read only<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
      C# auto-implemented properties<\/h2>\n\n\n\n
      If you have a property that requires no additional logic in the set<\/code> or get<\/code> accessors, you can use an auto-implemented property.<\/p>\n\n\n\n
      The following example defines the Skill<\/code> class that has two private fields name<\/code> and rating<\/code>, and the corresponding properties:<\/p>\n\n\n
      class<\/span> Skill<\/span>\n{\n    private<\/span> string<\/span> name;\n    private<\/span> sbyte<\/span> rating;\n\n    public<\/span> string<\/span> Name\n    {\n        get<\/span> { return<\/span> name; }\n        set<\/span> { name = value<\/span>; }\n\n    }\n    public<\/span> sbyte<\/span> Rating\n    {\n        get<\/span> { return<\/span> rating; }\n        set<\/span> { rating = value<\/span>; }\n    }\n\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
      Since the accessors of the properties have no additional logic besides reading from and writing to private fields, you can use auto-implemented properties like this:<\/p>\n\n\n
      class<\/span> Skill<\/span>\n{\n    public<\/span> string<\/span> Name { get<\/span>; set<\/span>; }\n    public<\/span> sbyte<\/span> Rating { get<\/span>; set<\/span>; }\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
      When the C# compiler encounters an auto-implemented property, it creates a private, anonymous field that can be accessed through the set<\/code> and get<\/code> accessors.<\/p>\n\n\n\n
      As you can see, the auto-implemented properties make the code more concise in this case.<\/p>\n\n\n\n
      In C# 9 or later, you can init an auto-implemented property like this:<\/p>\n\n\n
      class<\/span> Skill<\/span>\n{\n    public<\/span> string<\/span> Name { get<\/span>; set<\/span>; }\n    public<\/span> sbyte<\/span> Rating { get<\/span>; set<\/span>; } = 1<\/span>;\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
      In this example, we initialize the Rating<\/code> property so that its value is one when you create a new instance of the Skill class.<\/p>\n\n\n\n
      Summary<\/h2>\n\n\n\n
      • A property is a member of a class that provides a flexible way to read, write, or compute the value of a private field.<\/li>
      • A property contains get and\/or set accessors.<\/li>
      • The get accessor executes when you read the value from the property while the set accessor executes when you assign a value to the property.<\/li>
      • Use auto-implemented property if the get and set accessors have no additional logic to make the code more concise.<\/li><\/ul>\n
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