Hi Jamey,
If you could show us some code we might spot the errors.
If the fields are public they are visible to everyone, however, they will only be accessible through an instance of the class those fields belong to (unless the fields are static).
public class MyProgram
{
public static void Main()
{
MyForm myForm = new MyForm();
myForm.MyTextBo x.Text = "Hello World";
Application.Run (myForm);
}
}
public class MyForm : System.Windows. Forms.Form
{
public TextBox MyTextBox = new TextBox();
public MyForm()
{
this.Controls.A dd(MyTextBox);
}
}
The code above lets Main change the text of MyForm's MyTextBox. However, instead of accessing fields directly, you should go through properties..
public class MyProgram
{
public static void Main()
{
MyForm myForm = new MyForm();
myForm.MyText = "Hello World";
Application.Run (myForm);
}
}
public class MyForm : System.Windows. Forms.Form
{
private TextBox MyTextBox = new TextBox();
public string MyText
{
get{ return MyTextBox.Text; }
set{ MyTextBox.Text = value; }
}
public MyForm()
{
this.Controls.A dd(MyTextBox);
}
}
This way MyForm will have more control of what gets set in the TextBox. For instance, MyText can test for InvokeRequired before setting the TextBox value.
Having written all this, I think I understand your scenario
public class MyForm : System.Windows. Forms.Form
{
private TextBox MyTextBox = new TextBox();
private static TextBox MyStaticTextBox = new TextBox();
public string MyText
{
get{ return MyTextBox.Text; }
set{ MyTextBox.Text = value; }
}
public MyForm()
{
this.Controls.A dd(MyTextBox);
}
public static void Main()
{
MyTextBox.Text = "Hello World"; // ERROR! MyTextBox isn't static
MyStaticTextBox .Text = "Hello WOrld"; // Works because MyStaticTextBox is static
}
}
The code above won't work because Main() is static, which means you can't access fields, properties or methods from MyForm that aren't static. Among all MyForm objects you may create, there will be numerous MyTextBox controls created, one for each MyForm, but there will only be one MyStaticTextBox , shared among all the MyForm objects. For the same reason Main() needs to be static, so that the operating system can access the Main() method, even though there may be no MyForm objects created.
On Sun, 25 Mar 2007 09:55:06 +0200, Jamey Bon <jb***@ue.comwr ote:
I am a C# newbie. I am having a tough time with several issues of scope
and visibility.
In short, why can't I see any of the elements of Form1 (the base form
generated by the "Windows Application Project Wizard") from anywhere else
in my project? For example, why can I not change the text of a TextBox
control from Main() (which is, by default, in the Program class) even
after I have set its visibility to public in Form1? Furthermore, I can
add a class to the project, make sure it and its fields are public,
instantiate an object of that class (say, in Main()) but won't be ableto
see that class's public fields from within Form1. This seems to all hold
true even if I am using the fully qualified (starting with the namespace)
name.
This is actually a smaller part of my larger attempt to understand howto
organize a program into a decent object-oriented, modular design. I have
tried to find some good code samples of such, but so far have failed.
So, can someone please put me on the right track to understanding how the
visibility and scope is working in these cases? Thank you very much.
JB
--
Happy coding!
Morten Wennevik [C# MVP]
