Re: Enum within a button click event on a form - why compile error - C# Discussion Boards

Re: Enum within a button click event on a form - why compile error

14-Aug-06 6:42

private void button1_Click(object sender, EventArgs e)
{

enum MyTemp
{
cold = 0,
fp = 32
}

day1Miles.Text = textBox1.Text;

}

I get an error on 2 ( error says: } expected )

What am I missing in the concepts here? Why can't I define an enumerated constant at top of the button click? I can replace the enum statement with something like int cold = 0; and it works fine, so why can't I put an enum statement here?

For example this compiles without error:

private void button1_Click(object sender, EventArgs e)
{

int cold = 0;

day1Miles.Text = textBox1.Text;
}

-- modified at 12:49 Monday 14th August, 2006

Andrew Rissing14-Aug-06 7:00

Andrew Rissing

14-Aug-06 7:00

Try defining the enum outside of your function.

Re: Enum within a button click event on a form - why compile error

LuluSailor14-Aug-06 7:11

Re: Enum within a button click event on a form - why compile error

14-Aug-06 7:11

Defining the enum outside the function is exactly what is needed, but I just don't understand why I would need to define the enum outside of the function.

Rob Graham14-Aug-06 7:50

Re: Enum within a button click event on a form - why compile error

14-Aug-06 7:50

Because it is pointless to define the enum in that scope. It wouuld only be valid for the scope of the function, and useless outside of it (you could not pass in a parameter of the enum type, nor return a an object of the eunum's type.

LuluSailor14-Aug-06 9:16

Re: Enum within a button click event on a form - why compile error

14-Aug-06 9:16

Thank-you for trying to help, but I am still confused....
Maybe here are some better examples of my dilema in undertanding where I can define an enum? I know I can make the example work by moving where the enum is defined, but I still do not understand why it needs to be moved. Why can't the enum constant be used just like a symbolic constant as my examples below demonstrate?

This does NOT work..... I would think it would, and still cannot understand why not.

namespace ConsoleApplication2
{
class Program
{
static void Main(string[] args)
{
enum temps
{
cold = 0,
fp = 32
}

System.Console.WriteLine("freezing is {0}", (int)temps.fp);
}
}
}

But the following does compile...

namespace ConsoleApplication2
{
class Program
{
enum temps
{
cold = 0,
fp = 32
}

static void Main(string[] args)
{

System.Console.WriteLine("freezing is {0}", (int)temps.fp);
}
}
}

And this works, if ditch the idea of using an enum, and use named constants

namespace ConsoleApplication2
{
class Program
{
static void Main(string[] args)
{
int cold = 0;
int fp = 32;

System.Console.WriteLine("freezing is {0}", cold);
}
}
}

Dave Kreskowiak14-Aug-06 10:36

Dave Kreskowiak

14-Aug-06 10:36

Because the C# Language Specification says so. You can't do it because Enum's are an implementation of an abstract class (System.Enum), among other things. Since your really creating a concrete class by inheriting from System.Enum, you're bound by the rules of creating a new class. Classes can only be define at the Namespace and Class levels. You cannot define a class inside a method, so you can't define an Enum either.

Dave Kreskowiak
Microsoft MVP - Visual Basic

Re: Enum within a button click event on a form - why compile error

LuluSailor14-Aug-06 11:42

14-Aug-06 11:42

:-DAh makes sense now! Thank-you so much Dave and others too.

Just as a final blessing/followup. I thought I would try to show how classes cannot be defined within a method.

The example below does not compile - because you cannot define a class within a method ( you get the compile error: "} expected" on the line after the Main method) . And so the same problem would occur with the Enum - because you defining a class.

namespace ConsoleApplication2
{

class Program
{
static void Main(string[] args)
{
class temps
{
public int cold;
public int fp;

public temps()
{
cold = 0;
fp = 32;
}
}
temps xTemps = new temps();

System.Console.WriteLine("freezing is {0}", xTemps.fp);
}
}
}

If you move the definition of the class where it can legally be defined (in namespace or within another class - in this case I moved it to the namespace)... then all works well.

namespace ConsoleApplication2
{
class temps
{
public int cold;
public int fp;

public temps()
{
cold = 0;
fp = 32;
}
}
class Program
{
static void Main(string[] args)
{

temps xTemps = new temps();

System.Console.WriteLine("freezing is {0}", xTemps.fp);
}
}
}

system properties

Harikrk14-Aug-06 6:40

14-Aug-06 6:40

How can u get sytem properties like used memory, avilable free memmory total memory, processer spec etc using C#.net

Re: system properties

Rob Graham14-Aug-06 7:59

14-Aug-06 7:59

See the System.Management classes.

creating OCX

Harikrk14-Aug-06 5:27

14-Aug-06 5:27

How can i create OCX files in C#.Net... I want to use a custom control and make an OCX file from it(instead of dll).. can i?

Rob Graham14-Aug-06 5:42

14-Aug-06 5:42

No. You can, however, add the necessary registration code to your control, and then register if as a COM control and use it like an OCX..(it will need a strong name and must be installed to GAC)

Harikrk14-Aug-06 5:55

14-Aug-06 5:55

can u tell me how to create it using C#.net?
please provide some help if u have.

Rob Graham14-Aug-06 6:17

14-Aug-06 6:17

Any .Net DLL can be used as a COM object. There are a number of articles like this one[^] on Code project.

Harikrk14-Aug-06 6:22

14-Aug-06 6:22

i was asking can we create .ocx file for usercontrol as we does in vb 6.0?

Rob Graham14-Aug-06 7:32

14-Aug-06 7:32

You can create a user control as a dll and use it in non-C# code. see the article I linked (it discusses using the result in VB6), and search for COM interop. OCX is just a file extension It's the registry entries that matter.

Judah Gabriel Himango14-Aug-06 6:22

Judah Gabriel Himango

14-Aug-06 6:22

Right-click on your dll project in the Solution Explorer window within Visual Studio. Go to the "Build" tab. There is a checkbox on that page for "Register for COM Interop". Check that, and your .dll will automatically be registered for COM interop, meaning you could use it from COM.

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Judah Himango

Harikrk14-Aug-06 6:24

14-Aug-06 6:24

Ok.. thanks a lot