On the transfer parameters in C #

Let's just start with the code. We have here is a code, let's see why it takes that displays:

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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">class Program</span> class Program</span> <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">{</span> {</span>     <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">static void Main(string[] args)</span> static void Main (string [] args)</span>     <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">{</span> {</span>         <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">int a = 1;</span> int a = 1;</span>         <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">ProcessValue(a);</span> ProcessValue (a);</span>         <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">Console.WriteLine(a.ToString());</span> Console.WriteLine (a.ToString ());</span>         <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">//здесь будет выведено 1</span> // this will 1</span>         <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">TestClass test = new TestClass();</span> TestClass test = new TestClass ();</span>         <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">test.val = 2;</span> test.val = 2;</span>         <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">ProcessRef(test);</span> ProcessRef (test);</span>         <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">Console.WriteLine(test.val.ToString());</span> Console.WriteLine (test.val.ToString ());</span>         <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">//здесь будет выведено 10</span> // this will 10</span>         <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">TestClass test = new TestClass();</span> TestClass test = new TestClass ();</span>         <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">test.val = 3;</span> test.val = 3;</span>         <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">Process(test);</span> Process (test);</span>         <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">Console.WriteLine(test.val.ToString());</span> Console.WriteLine (test.val.ToString ());</span>         <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">//а здесь будет выведено 3</span> // and here will be displayed 3</span>     <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">}</span> }</span>     <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">static void ProcessValue(int par)</span> static void ProcessValue (int par)</span>     <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">{</span> {</span>         <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">par = 3;</span> par = 3;</span>     <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">}</span> }</span>     <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">static void ProcessRef(TestClass par)</span> static void ProcessRef (TestClass par)</span>     <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">{</span> {</span>         <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">par.val = 10;</span> par.val = 10;</span>     <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">}</span> }</span>     <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">static void Process(TestClass par)</span> static void Process (TestClass par)</span>     <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">{</span> {</span>         <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">par = new TestClass();</span> par = new TestClass ();</span>         <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">par.val = 100;</span> par.val = 100;</span>     <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">}</span> }</span> <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">}</span> }</span> <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">public class TestClass</span> public class TestClass</span> <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">{</span> {</span>     <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">public int val;</span> public int val;</span> <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">}</span> }</span>

You probably know that there are significant .Net (value) and reference (reference) types. The first - completely accommodated in the stack, and the second placed in the managed heap and the stack pointer is placed only on them.

The second useful knowledge, which many unfortunately do not always know or understand is that all of the default settings are passed into methods by value, that is, simply put, is copied.
That is, the transfer of the object as a parameter value type, the stack is created exactly the same object and when transferring an object reference type the same thing happens. But, if in case of a significant type of object in the stack and so is the value in the object reference type in the stack is only a reference to the object itself, respectively, within the method the changes occurring therein also. Here is an illustration of the process:

Why, then, in the third case, the result will be 3 instead of 100? All the same, because the values ​​are transferred to a copy. That is, at the time of the assignment within the function Process stack we will look something like this.

I'm a little incorrectly painted the same arrows, as the transmission parameter to the function initial link is copied, and when an object inside the function changes the reference itself, but the essence of what is happening is reflected correctly - all actions within the function occur with a copy of the pointer to the object, and not with the index. That is, test both pointed object val = 3, so it and points. Here is another picture - a stack at the time of the method Process ()

Pi output from Precess () all that has been created inside the method goes out of scope and is destroyed and what was before entering it. That is, in this case, object val = 3.

And how to do that and in the third case, after you exit the Process () Our facility contains a new value? Make it easy enough to use to define the method and its call to the ref keyword

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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">class Program</span> class Program</span> <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">{</span> {</span>     <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">static void Main(string[] args)</span> static void Main (string [] args)</span>     <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">{</span> {</span>         <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">TestClass test = new TestClass();</span> TestClass test = new TestClass ();</span>         <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">test.val = 3;</span> test.val = 3;</span>         <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">Process(ref test);</span> Process (ref test);</span>         <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">Console.WriteLine(test.val.ToString());</span> Console.WriteLine (test.val.ToString ());</span>         <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">//теперь результат - 100</span> // now the result - 100</span>     <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">}</span> }</span>          <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">static void Process(ref TestClass par)</span> static void Process (ref TestClass par)</span>     <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">{</span> {</span>         <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">par = new TestClass();</span> par = new TestClass ();</span>         <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">par.val = 100;</span> par.val = 100;</span>     <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">}</span> }</span> <span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">}</span> }</span>

Now the parameter to the method Process () will be passed by reference, that is par will not be a copy of the test (ie, a pointer to the memory area that hosts the object), and a pointer to the pointer, so all changes made to the parameter within the method will not occur with a copy of the object, and with itself. 

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