Property lost when another class call it

Question

2.50/5 (2 votes)

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i have three class. First Class where i declare property,in second class i set prperty value and third class for use its value.but in third class property is empty.
class1

C#

class first
{
public string first{get; set;}
}

class2

XML

class second
{
public second()
{
  first f1=new first();
  f1.first="hello";
}
}
</pre>

class third

XML

class third
{
public third()
{
  first f1=new first();
  string nn=f1.first;
}
}

string nn show null. what should i do?

Posted 6-Feb-15 10:09am

ssnk

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2 solutions

Solution 2

If you want Forms to have access to the value (contents) of a Field/Property (variable) in another Form, then you have two essential choices:

1. make the Field/Property in the Form you wish to share 'static: then that Field becomes a Field of the Class, rather than a Field of each instance of the Class.

C#

public class FirstClass
{
    public static string FirstString {get; set;}
}

public class SecondClass
{
    string valueOfFirstStringInFirst = FirstClass.FirstString;
}

// test it
FirstClass fc = new FirstClass();
FirstClass.FirstString = "hello";
SecondClass sc = new SecondClass();
Console.WriteLine(sc.valueOfFirstStringInFirst);

Notice that you had to access the static Property 'FirstString using the Class name, not the name of the instance ('fc) of the Class.

2. Other ways for one Class to access the values (contents) of Fields/Whatever in another Class which do not involve using static include:

a. by using Interfaces which both Classes implement
b. by injecting references to instances into instances of other Classes
c. by exposing public methods that indirectly access the value (contents)

Posted 7-Feb-15 0:01am

BillWoodruff

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**Zoltán Zörgő** · Accepted Answer · 2015-02-06T10:23:00

Solution 1

In second you create an instance of first. I third you create an other instance of first. These are two different instances. The property is not static, thus every instance has a different memory space allocated for it. Sou either share one single instance or use static property.
But I can't tell you which path to choose, as your post is rather theoretic.

Posted 6-Feb-15 10:23am

Zoltán Zörgő

v2

Comments

ZurdoDev 6-Feb-15 16:27pm

+5. Good explanation.

ssnk 6-Feb-15 16:35pm

how can i share single instance in diffrent class

Zoltán Zörgő 6-Feb-15 16:39pm

It really depends on how you intend to use them. The code posted tells us nothing at all. Sorry, I can't guide you further without something much more concrete.

ssnk 6-Feb-15 16:49pm

its a wpf application
code:-
variable class-
public class Variable
{
public string content { get; set; }
}

page1
private void btn1_Click(object sender, RoutedEventArgs e)
{
Variable v =new Variable();
v.content = textbox1.Text;
Page2 p2 = new Page2();
this.NavigationService.Navigate(p2);
}
page2
public Page2()
{
InitializeComponent();
Variable v = new Variable();
textbox2.Text = v.content;
}

Zoltán Zörgő 6-Feb-15 16:59pm

A) Extend Page2 with a parametrized constructor and pass v to it.
B) Add a property of type Variable with public setter to Pare2 and set it to v after you create it in that click method. But be aware not to create a new instance afterwards. In this case you won't be able to set the textbox text in the constructor, you have to put that in the setter.

ssnk 6-Feb-15 17:08pm

thanks for solution.
but i can't pass parameter because property almost above ten.

Zoltán Zörgő 6-Feb-15 17:18pm

I don't understand this.

ssnk 6-Feb-15 17:29pm

actually i have many value to pass.instead one property i have
many property and that i want pass page1 to page2. so what do i have to do?

Zoltán Zörgő 6-Feb-15 17:33pm

Embed them all in that "Variable" class. You can have as many properties as you like. Than you can pass a single object only. Why is this a problem? I don't think you have any other option.

ssnk 6-Feb-15 17:36pm

ok thanks

ssnk 6-Feb-15 17:35pm

like i have 10 property,every property assign a different value on page1 and i want to use that 10 property in page2. how?

Sergey Alexandrovich Kryukov 7-Feb-15 2:39am

5ed.
—SA