从Form1将值设置为Class1中的属性，然后使用C＃Windows Form将Class1中的该属性的值获取到Form2

Question

I have this problem, i've set a value to a property from shall we say Form1, then get that value in Form2 but it return null.

sample code.

//Sample.cs
public class Sample
{
    private string exchange;

    public Sample()
    {
    }

    public string Exchange
    {
        get { return exchange; }
        set { exchange = value; }
    }
}

//From Form1 set value
private void setBtn_Click_1(object sender, EventArgs e)
{
    Sample testing = new Sample();

    testing.Exchange = exchange.Text;
}

//From Form2 get value
private void getBtn_Click_1(object sender, EventArgs e)
{
    Sample testing2 = new Sample();
    string exchange2 = testing2.Exchange;
}

Here's the problem, exchange2 have a value of null, i know its because i declared a new instance, please tell me how to get the value using Form2 that have been set in Form1.

Thanks in advance guys!

Answer 1

It is OK return null because you each time create a new object

Sample testing2 = new Sample();

declare the public property in Form2 class

  class Form2
  {
     public Sample MySample {get; set;}
  }
private void setBtn_Click_1(object sender, EventArgs e)
{
Sample testing = new Sample();

Form2 form2 = new Form2();
form2.MySample = testing;
form2.Show();
}

Answer 2

If you want to use classes and properties in this way make exchange field static so it will be shared among all instances of your class. Static fields are class related and not instances related and in your case from Form1 and Form2 you are creating different instances of class.

Answer 3

Following are few posibilites:

1) Delcare the property static:

public static string Exchange{get;set;}

2) Pass the object created in Form1 in some way to Form2: