blocks|key|691621|text|你是如何将对象传递给方法的？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|691622|你是否在object的方法中做了一些新的事情？如果是这样的话，你必须在方法中使用ref。|offset|length|style|CODE|691623|下面的链接给了你更好的想法。|691624|http://dotnetstep.blogspot.com/2008/09/passing-reference-type-byval-or-byref.html|691625|entityMap|0|LINK|mutability|MUTABLE|url^0|0|14|3|0|0|0|29|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@$D|U|E|V|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|W|8|@]|9|@]|A|$]]|$1|J|3|K|5|6|7|X|8|@]|9|@$D|Y|E|Z|1|10]]|A|$]]|$1|L|3|-4|5|6|7|11|8|@]|9|@]|A|$]]]|M|$N|$5|O|P|Q|A|$R|K]]]]

How did you pass object to method?

Are you doing new inside that method for object? If so, you have to use <code>ref</code> in method.

Following link give you better idea.

<a href="http://dotnetstep.blogspot.com/2008/09/passing-reference-type-byval-or-byref.html" rel="nofollow noreferrer">http://dotnetstep.blogspot.com/2008/09/passing-reference-type-byval-or-byref.html</a>

blocks|key|475503|text|当您将System.Drawing.Image类型对象传递给某个方法时，实际上是在传递该对象的引用副本。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|475504|因此，如果在该方法中，您正在加载使用new/copied引用加载的新图像。您不能在原始版本中进行更改。|475505|YourMethod(System.Drawing.Image+image)
{
++++//now+this+image+is+a+new+reference
++++//if+you+load+a+new+image+
++++image+=+new+Image()..
++++//you+are+not+changing+the+original+reference+you+are+just+changing+the+copy+of+original+reference
}|code-block|syntax|javascript|475506|entityMap^0|3|K|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|R|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|S|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|N|$]]

When you pass the the <code>System.Drawing.Image</code> type object to a method you are actually passing a copy of reference to that object.

So if inside that method you are loading a new image you are loading using new/copied reference. You are not making change in original.

<pre><code>YourMethod(System.Drawing.Image image)
{
 //now this image is a new reference
 //if you load a new image 
 image = new Image()..
 //you are not changing the original reference you are just changing the copy of original reference
}
</code></pre>

blocks|key|475544|text|在按引用传递时，您只需在函数参数中添加"ref“，而且还应该声明函数"static”，因为main是静态的(#public+void+main(String[]+args))！|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|475545|namespace+preparation
{
++public++class+Program
++++{
++++++public+static+void+swap(ref+int+lhs,ref+int+rhs)
++++++{
++++++++++int+temp+=+lhs;
++++++++++lhs+=+rhs;
++++++++++rhs+=+temp;
++++++}
++++++++++static+void+Main(string[]+args)
++++++++{
++++++++++++int+a+=+10;
++++++++++++int+b+=+80;

++Console.WriteLine("a+is+before+sort+"+%2B+a);
++++++++++++Console.WriteLine("b+is+before+sort+"+%2B+b);
++++++++++++swap(ref+a,+ref+b);
++++++++++++Console.WriteLine("");
++++++++++++Console.WriteLine("a+is+after+sort+"+%2B+a);
++++++++++++Console.WriteLine("b+is+after+sort+"+%2B+b);++
++++++++}
++++}
}|code-block|syntax|javascript|475546|entityMap^0|1J|V|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

In Pass By Reference You only add "ref" in the function parameters and one 
more thing you should be declaring function "static" because of main is static(#<code>public void main(String[] args)</code>)! 

<pre><code>namespace preparation
{
 public class Program
 {
 public static void swap(ref int lhs,ref int rhs)
 {
 int temp = lhs;
 lhs = rhs;
 rhs = temp;
 }
 static void Main(string[] args)
 {
 int a = 10;
 int b = 80;

 Console.WriteLine("a is before sort " + a);
 Console.WriteLine("b is before sort " + b);
 swap(ref a, ref b);
 Console.WriteLine("");
 Console.WriteLine("a is after sort " + a);
 Console.WriteLine("b is after sort " + b); 
 }
 }
}
</code></pre>

blocks|key|691773|text|在最新版本的C#中，即撰写本文时的C#+9中，对象默认由ref传递。因此，对调用函数中的对象所做的任何更改都将保留在被调用函数中的对象中。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|691774|entityMap^0|S|3|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

In the latest version of C#, which is C# 9 at this time of writing, objects are by default passed by <code>ref</code>. So any changes made to the object in the calling function will persist in the object in the called function.

blocks|key|691790|text|Employee+e+=+new+Employee();
e.Name+=+"Mayur";

//Passes+the+reference+as+value.+Parameters+passed+by+value(default).
e.ReferenceParameter(e);

Console.WriteLine(e.Name);+//+It+will+print+"Shiv"

+class+Employee+{

+++public+string+Name+{+get;+set;+}

+++public+void+ReferenceParameter(Employee+emp)+{

+++++//Original+reference+value+updated.
++++emp.Name+=+"Shiv";

++++//+New+reference+created+so+emp+object+at+calling+method+will+not+be+updated+for+below+changes.
++++emp+=+new+Employee();
++++emp.Name+=+"Max";
++}
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|691791|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>Employee e = new Employee();
e.Name = &quot;Mayur&quot;;

//Passes the reference as value. Parameters passed by value(default).
e.ReferenceParameter(e);

Console.WriteLine(e.Name); // It will print &quot;Shiv&quot;

 class Employee {

 public string Name { get; set; }

 public void ReferenceParameter(Employee emp) {

 //Original reference value updated.
 emp.Name = &quot;Shiv&quot;;

 // New reference created so emp object at calling method will not be updated for below changes.
 emp = new Employee();
 emp.Name = &quot;Max&quot;;
 }
}
</code></pre>

In C#, I have always thought that non-primitive variables were passed by reference and primitive values passed by value.

So when passing to a method any non-primitive object, anything done to the object in the method would effect the object being passed. (C# 101 stuff)

However, I have noticed that when I pass a System.Drawing.Image object, that this does not seem to be the case? If I pass a system.drawing.image object to another method, and load an image onto that object, then let that method go out of scope and go back to the calling method, that image is not loaded on the original object?

Why is this?

Passing Objects By Reference or Value in C#

在C#中，我一直认为非原语变量是通过引用传递的，而原始值是通过值传递的。因此，当向方法传递任何非基元对象时，方法中对该对象所做的任何操作都会影响所传递的对象。(C# 101资料)然而，我注意到，当我传递一个System.Drawing.Image对象时，情况似乎并非如此？如果我将一个system.drawing.ima...

问在C#中通过引用或值传递对象
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