When an object is passed to a method the method receives a reference to the object?
Skip to main content This browser is no longer supported. Show
Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support. Method Parameters (C# Reference)
In this articleIn C#, arguments can
be passed to parameters either by value or by reference. Remember that C# types can be either reference types (
Because a struct is a value type, when you pass a struct by value to a method, the method receives and operates on a copy of the struct argument. The method has no access to the original struct in the calling method and therefore can't change it in any way. The method can change only the copy. A class instance is a reference type, not a value type. When a reference type is passed by value to a method, the method receives a copy of the reference to the class instance. That is, the called method receives a copy of the address of the instance, and the calling method retains the original address of the instance. The class instance in the calling method has an address, the parameter in the called method has a copy of the address, and both addresses refer to the same object. Because the parameter contains only a copy of the address, the called method cannot change the address of the class instance in the calling method. However, the called method can use the copy of the address to access the class members that both the original address and the copy of the address reference. If the called method changes a class member, the original class instance in the calling method also changes. The output of the following example illustrates the difference. The value of the
How an argument is passed, and whether it's a reference type or value type controls what modifications made to the argument are visible from the caller. Pass a value type by valueWhen you pass a value type by value:
The following example demonstrates passing value-type parameters by value. The variable
The variable Pass a value type by referenceWhen you pass a value type by reference:
The following example is the same as the previous example, except that the argument is passed as a
In this example, it is not the value of Pass a reference type by valueWhen you pass a reference type by value:
The
following example demonstrates passing a reference-type parameter,
In the preceding example, the array, Pass a reference type by referenceWhen you pass a reference type by reference:
The following example is the same as the previous example, except that the
All of the changes that take place inside
the method affect the original array in Scope of references and valuesMethods can store the values of parameters in fields. When parameters are passed by value, that's always safe. Values are copied, and reference types are reachable when stored in a field. Passing parameters by reference safely requires the compiler to define when it's safe to assign a reference to a new variable. For every expression, the compiler defines a scope that bounds access to an expression or variable. The compiler uses two scopes: safe_to_escape and ref_safe_to_escape.
Informally, you can think of these scopes as the mechanism to ensure your code never accesses or modifies a reference that's no longer valid. A reference is valid as long as it refers to a valid object or struct. The safe_to_escape scope defines when a variable can be assigned or reassigned. The ref_safe_to_escape scope defines when a variable can ref assigned or ref reassigned. Assignment assigns a variable to a new value; ref assignment assigns the variable to refer to a different storage location. ModifiersParameters declared for a method without in,
ref or out, are passed to the called method by value. The
This section describes the keywords you can use when declaring method parameters:
See also
FeedbackSubmit and view feedback for When an object is passed to a method what is actually passed?To state this more fully, when an object is passed into a method as a parameter, a copy of the variable on the stack containing the reference to the object is passed. And it's this variable on the stack that is passed by value.
When we pass an object by reference which is called?Explanation: The location of the object, that is, the exact memory location is passed, when the object is passed by reference. The pass by reference is actually a reference to the object that the function uses with another name to the same memory location as the original object uses. 11.
When an object is passed as an argument it is actually a reference to the object that is passed True False?When an object, such as a String , is passed as an argument, it is actually a reference to the object that is passed. The contents of a String object cannot be changed. When passing multiple arguments to a method, the order in which the arguments are passed is not important.
What happens when an object is passed by reference in Java?A mutable object's value can be changed when it is passed to a method. An immutable object's value cannot be changed, even if it is passed a new value. “Passing by value” refers to passing a copy of the value. “Passing by reference” refers to passing the real reference of the variable in memory.
|