{"id":275,"date":"2022-01-03T09:15:50","date_gmt":"2022-01-03T02:15:50","guid":{"rendered":"https:\/\/csharptutorial.net\/?page_id=275"},"modified":"2022-01-05T09:17:15","modified_gmt":"2022-01-05T02:17:15","slug":"csharp-this","status":"publish","type":"page","link":"https:\/\/www.csharptutorial.net\/csharp-tutorial\/csharp-this\/","title":{"rendered":"C# this"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll learn about C# this<\/code> keyword and how to use it effectively.<\/p>\n\n\n\n

What is this keyword in C#<\/h2>\n\n\n\n

A class<\/a> is a blueprint for creating objects. To reference the current object inside the class, you use the this<\/code> keyword. Therefore, the this<\/code> keyword refers to the current instance of the class.<\/p>\n\n\n\n

To explicitly reference a field inside a method of a class, you use the this<\/code> keyword, followed by the dot operator (.<\/code>), and the field name like this:<\/p>\n\n\n

this<\/span>.FieldName<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
Likewise, you can use the this<\/code> keyword to explicitly call a method in another method of the class:<\/p>\n\n\n
this<\/span>.MethodName(arguments)<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
C# this keyword example<\/h2>\n\n\n\n
The following example defines the Person<\/code> class with the fields FirstName<\/code> and LastName<\/code> and two methods GetFullName()<\/code> and SayHi()<\/code>:<\/p>\n\n\n
\/\/ Person.cs<\/span>\n\nclass<\/span> Person<\/span>\n{\n    public<\/span> string<\/span> FirstName;\n    public<\/span> string<\/span> LastName;\n\n    public<\/span> string<\/span> GetFullName<\/span>(<\/span>)<\/span>\n    {\n        return<\/span> $\"{this<\/span>.FirstName}<\/span> {this<\/span>.LastName}<\/span>\"<\/span>;\n    }\n    public<\/span> string<\/span> SayHi<\/span>(<\/span>)<\/span>\n    {\n        return<\/span> $\"Hi, I'm {this<\/span>.GetFullName()}<\/span>.\"<\/span>;\n    }\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
In this example, we use the this<\/code> keyword to reference the FirstName<\/code> and LastName<\/code> fields in the GetFullName()<\/code> method. Also, we use the this<\/code> keyword to call the GetFullName()<\/code> method in the SayHi()<\/code> method.<\/p>\n\n\n\n
The following creates a new instance of the Person<\/code> class and call the SayHi()<\/code> method:<\/p>\n\n\n
\/\/ Program.cs<\/span>\n\n\/\/ Create a new instance of the Person class<\/span>\nPerson p1 = new<\/span>();\np1.FirstName = \"John\"<\/span>;\np1.LastName = \"Doe\"<\/span>;\n\n\/\/ Show the fullname<\/span>\nConsole.WriteLine(p1.GetFullName());\n\n\/\/ Display the greeting<\/span>\nConsole.WriteLine(p1.SayHi());<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
When calling the p1.GetFullName()<\/code> method, the this<\/code> keyword references the p1<\/code> object. So the FirstName<\/code> and LastName<\/code> fields are \"John\"<\/code> and \"Doe\"<\/code> respectively.<\/p>\n\n\n\n
The SayHi()<\/code> method calls the GetFullName()<\/code> method via the this<\/code> keyword. Therefore, the p1.GetFullName()<\/code> method returns the \"John Doe\"<\/code> string. Hence, the SayHi()<\/code> method returns the string \"Hi, I'm John Doe.\"<\/code>.<\/p>\n\n\n\n
Using C# this keyword for method chaining<\/h2>\n\n\n\n
The following example adds two new methods SetFirstName()<\/code> and SetLastName()<\/code> to the Person<\/code> class:<\/p>\n\n\n
\/\/ Person.cs<\/span>\n\nclass<\/span> Person<\/span>\n{\n    public<\/span> string<\/span> FirstName;\n    public<\/span> string<\/span> LastName;\n\n    public<\/span> string<\/span> GetFullName<\/span>(<\/span>)<\/span>\n    {\n        return<\/span> $\"{this<\/span>.FirstName}<\/span> {this<\/span>.LastName}<\/span>\"<\/span>;\n    }\n\n    public<\/span> string<\/span> SayHi<\/span>(<\/span>)<\/span>\n    {\n        return<\/span> $\"Hi, I'm {this<\/span>.GetFullName()}<\/span>.\"<\/span>;\n    }\n\n    public<\/span> Person SetFirstName<\/span>(string<\/span> firstName<\/span>)<\/span>\n    {\n        this<\/span>.FirstName = firstName;\n        return<\/span> this<\/span>;\n    }\n\n    public<\/span> Person SetLastName<\/span>(string<\/span> lastName<\/span>)<\/span>\n    {\n        this<\/span>.LastName = lastName;\n        return<\/span> this<\/span>;\n\n    }\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
In this example, the SetFirstName()<\/code> and SetLastName()<\/code> methods assign their arguments to the FirstName<\/code> and LastName<\/code> fields and return the current instance of the Person<\/code> class. <\/p>\n\n\n\n
The following creates a new Person<\/code> object, calls the SetFirstName()<\/code>, SetLastName()<\/code>, and SayHi()<\/code> methods:<\/p>\n\n\n
\/\/ Program.cs<\/span>\n\nPerson p1 = new<\/span>();\n\np1.SetFirstName(\"John\"<\/span>);\np1.SetLastName(\"Doe\"<\/span>);\nstring<\/span> greeting = p1.SayHi();\n\nConsole.WriteLine(greeting);<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
Since both SetFirstName()<\/code> and SetLastName()<\/code> methods return the current Person<\/code>‘s object, you can replace three statements with one statement as follows:<\/p>\n\n\n
\/\/ Program.cs<\/span>\n\n\nPerson p1 = new<\/span>();\n\nstring<\/span> greeting = p1.SetFirstName(\"John\"<\/span>)\n                    .SetLastName(\"Doe\"<\/span>)\n                    .SayHi();\n\nConsole.WriteLine(greeting);<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
This technique is called method chaining<\/strong>.<\/p>\n\n\n\n
How it works.<\/p>\n\n\n\n
The SetFirstName()<\/code> method returns this<\/code> that is the p1<\/code> object:<\/p>\n\n\n
p1.SetFirstName(\"John\"<\/span>);<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
However, you don’t need to use an immediate variable to store the p1. And you can immediately call SetLastName()<\/code> of the p1<\/code> object like this:<\/p>\n\n\n
p1.SetFirstName(\"John\"<\/span>)\n  .SetLastName(\"Doe\"<\/span>);<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
Since the SetLastName()<\/code> method also returns this<\/code> that is the p1<\/code> object, you can call the SayHi()<\/code> method on it immediately. Because the SayHi()<\/code> method returns a string, you can assign it to the greeting<\/code> variable:<\/p>\n\n\n
\/\/ Program.cs<\/span>\n\nPerson p1 = new<\/span>();\n\nstring<\/span> greeting = p1.SetFirstName(\"John\"<\/span>)\n                    .SetLastName(\"Doe\"<\/span>)\n                    .SayHi();\n\nConsole.WriteLine(greeting);<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
Summary<\/h2>\n\n\n\n
  • The C# this<\/code> keyword refers to the current object of the class.<\/li>
  • Use C# this<\/code> keyword for method chaining to make the code more concise.<\/li><\/ul>\n
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