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this (C# Reference) 

The this keyword refers to the current instance of the class.

The following are common uses of this:

  • To qualify members hidden by similar names, for example:

    public Employee(string name, string alias) 
    {
        this.name = name;
        this.alias = alias;
    } 
    
  • To pass an object as a parameter to other methods, for example:

    CalcTax(this);
    
  • To declare indexers, for example:

    public int this [int param]
    {
        get { return array[param];  }
        set { array[param] = value; }
    }
    

Static member functions, because they exist at the class level and not as part of an object, do not have a this pointer. It is an error to refer to this in a static method.

In this example, this is used to qualify the Employee class members, name and alias, which are hidden by similar names. It is also used to pass an object to the method CalcTax, which belongs to another class.

// keywords_this.cs
// this example
using System;
class Employee
{
    private string name;
    private string alias;
    private decimal salary = 3000.00m;

    // Constructor:
    public Employee(string name, string alias)
    {
        // Use this to qualify the fields, name and alias:
        this.name = name;
        this.alias = alias;
    }

    // Printing method:
    public void printEmployee()
    {
        Console.WriteLine("Name: {0}\nAlias: {1}", name, alias);
        // Passing the object to the CalcTax method by using this:
        Console.WriteLine("Taxes: {0:C}", Tax.CalcTax(this));
    }

    public decimal Salary
    {
        get { return salary; }
    }
}
class Tax
{
    public static decimal CalcTax(Employee E)
    {
        return 0.08m * E.Salary;
    }
}

class MainClass
{
    static void Main()
    {
        // Create objects:
        Employee E1 = new Employee("John M. Trainer", "jtrainer");

        // Display results:
        E1.printEmployee();
    }
}

Name: John M. Trainer
Alias: jtrainer
Taxes: $240.00

For additional examples, see class and struct.

For more information, see the following sections in the C# Language Specification:

  • 7.5.7 this access

  • 10.2.6.4 this access

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