C# Discussion Boards - CodeProject

Richard Lowe15-Oct-03 10:36

Richard Lowe

15-Oct-03 10:36

First, you *can* do bitwise ops on Enum values without casting, but you might want to mark the enum with the FlagsAttribute if you do so (which VS.NET, at least, uses in some cases).

Since enums can be defined as various at various int sizes and signed or unsigned, that implicit cast would have to follow the enum's int type or risk a lossy cast (can't cast to Int32 from Int64 without a loss of data similar with unit to int). I prefer the type safety and un-ambiguity, and if you need it, the int value is there.

R.

Alvaro Mendez15-Oct-03 11:10

Alvaro Mendez

15-Oct-03 11:10

Richard Lowe wrote:
First, you *can* do bitwise ops on Enum values without casting, but you might want to mark the enum with the FlagsAttribute if you do so (which VS.NET, at least, uses in some cases).

Um, no. It doesn't work. Tell me if this compiles for you:

[Flags]
enum e { e0, e1, e2 };
 
void foo()
{
  int i = e.e1 | e.e2;
  bool b = (i & e.e1) != 0;
}

Richard Lowe wrote:
Since enums can be defined as various at various int sizes and signed or unsigned, that implicit cast would have to follow the enum's int type or risk a lossy cast (can't cast to Int32 from Int64 without a loss of data similar with unit to int). I prefer the type safety and un-ambiguity, and if you need it, the int value is there.

Hmmm, it may be that I've gotten used to employing enums for more than what they're really designed for. I guess I'll have to revert back to the Java way: use const ints. Sigh | :sigh:

Regards,
Alvaro

Can I ask you a question?

Heath Stewart15-Oct-03 11:52

Heath Stewart

15-Oct-03 11:52

Alvaro Mendez wrote:
[Flags]enum e { e0, e1, e2 }; void foo(){ int i = e.e1 | e.e2; bool b = (i & e.e1) != 0;}

No, but this does:

e = e.e1 | e.e2;
bool b = (e & e.e1) != 0;

I do it all the time.

-----BEGIN GEEK CODE BLOCK-----
Version: 3.21
GCS/G/MU d- s: a- C++++ UL@ P++(+++) L+(--) E--- W+++ N++ o+ K? w++++ O- M(+) V? PS-- PE Y++ PGP++ t++@ 5 X+++ R+@ tv+ b(-)>b++ DI++++ D+ G e++>+++ h---* r+++ y+++
-----END GEEK CODE BLOCK-----

Alvaro Mendez15-Oct-03 13:04

Alvaro Mendez

15-Oct-03 13:04

Yeah, that's nice.

Unfortunately, this forces you to predefine all your bit values in the same enum. If you then create a derived class with an extended set of bits, inside its own enum, you can't AND or OR those to the base class's. You follow me? In other words, for class hierarchies this doesn't work. If enum types could be derived, it'd be another story, but...

Regards,
Alvaro

Can I ask you a question?

bjoernen16-Oct-03 3:36

bjoernen

16-Oct-03 3:36

C# enums are not primarily used for giving integer constants names. For that purpose you use integer constants. Enums are a type of their own. Thats why they have to be casted if you want to use them as integers. That, together with not treating 0/1 as boolean values, are just ways to improve the language and enforce type safety, that makes us programmers write safer code.

Your examples of bitwise operations dont work because you try to implicitly convert to Int32.

Custom Controls and Enum value Types

Richard Lowe16-Oct-03 3:37

Richard Lowe

16-Oct-03 3:37

A bitwise operation on one Enum to another Enum yields *an Enum* - not an int. They keep their type safety. So assign the result to an Enum and it works.

Toolbar

Gary Kirkham15-Oct-03 8:50

Gary Kirkham

15-Oct-03 8:50

I am handling the MouseHover event for my toolbar. I would like to find out which button in the toolbar the mouse cursor is hovering over. How do I determine this?

Gary Kirkham

A working Program is one that has only unobserved bugs

I thought I wanted a career, turns out I just wanted paychecks

Re: Toolbar

Heath Stewart15-Oct-03 11:54

Heath Stewart

15-Oct-03 11:54

With the BCL ToolBar class, you have to get the mouse coordinates (this is easy), convert to client coordinates in relation to the toolbar (call PoingToClient on the toolbar instance) and enumerate your toolbar buttons to find out over which the point lies.

For most applications, I recommend you go with a decent 3rd-party toolbar. They have a lot more functionality.

Douglas Troy15-Oct-03 5:45

Passing a Form reference to a new Form

15-Oct-03 5:45

The Scenario

I've created a custom control that has a public property that is of an enumerated value type. I have created an accessor method to get/set that property and have it 'binded'. Finally, in the constructor for the control, I set that property to a default value, referencing the full namespace of the enum value type to ensure no conflicts with other controls would exist (see sample code below):

<br />
namespace MyControls {<br />
<br />
  public class MyCustomControl : System.Windows.Forms.Label <br />
  {<br />
    public enum MyLabelType { High, Low, Special, Hidden };<br />
<br />
    private MyLabelType myLabelType;<br />
<br />
    // constructor<br />
    public MyCustomControl <br />
    {<br />
       // set default value<br />
       myLabelType = MyControls.MyCustomControl.MyLabelType.Special;<br />
    }<br />
<br />
  ...<br />
<br />
    // public accessor<br />
    [Bindable(true), Category("Custom Properties"),<br />
     Description("My Custom Control ...")]<br />
    public MyControls.MyCustomControl.MyLabelType LabelType<br />
    {<br />
      get ... <br />
      set ...<br />
    } <br />
<br />
...<br />
<br />
  }<br />
}<br />

The Problem

I drop the custom control onto a form and set my properties without a hitch. I add a using clause to my code for that namespace and do a build. I get no errors, I can run the application without issues ... Etc. However, if I close the solution/project, and open it back up, then open that form back up in design mode, I get errors on that enumerated property that indicates "The variable 'MyLabelType' is either undeclared or was never assigned".

When I attempt to set a variable to this value type my code, the intellisense doesn't "find" the enum value type. (Example):

MyControls.MyCustomControl.MyLabelType is not found ...

Yet if I open custom control solution in studio, rebuild it, and then go BACK to my solution that uses the custom control, studio can now "see" the enumerated data type ...

I have tried to set the "DefaultValue" on the property accessor for this type, but to no avail. It does not seem to affect the outcome.

Any suggestions or answers as to what I am doing wrong, or to why this is happening? I'm guessing the solution is something simple that I am just overlooking. Sigh | :sigh:

TIA

D.

mikemilano15-Oct-03 4:50

mikemilano

15-Oct-03 4:50

I'm trying to pass a reference of Form1 to Form2 so I can change things on Form1 from Form2.

Here is my logic:
Form1

private void btnShow_Click(object sender, System.EventArgs e)
{
  FormTwo = new Form2(ref this);
  FormTwo.Show();
}

Form2:

// .. yes form one was declared up here somewhere as public
public Form2(ref Form1 PassingForm)
{
  InitializeComponent();

  FormOne = PassingForm;
}

error CS1605: Cannot pass '<this>' as a ref or out argument because it is read-only

i can read the error, .. but what would the proper logic be here?

Re: Passing a Form reference to a new Form

Mike Dimmick15-Oct-03 4:59

Mike Dimmick

15-Oct-03 4:59

You don't need 'ref', because a Form1 is already a reference type. The error occurs because you're trying to pass a reference to 'this', which cannot be changed.

Personally I find reference languages confusing, because of the nature of aliasing and that there are no clues in the syntax indicating whether you're dealing with a value (which uses a shallow copy) or a reference (which merely copies the reference).

BindingContext

Anonymous15-Oct-03 4:45

Anonymous

15-Oct-03 4:45

Hey,

I have a listview bounded to a dataset.
I have also 2 textboxes. These textboxes are in the same listview.bindingcontext.

listview.BindingContext = new BindingContext();
txt1.BindingContext = listview.BindingContext;
txt2.BindingContext = listview.BindingContext;

The listview has an event : selectedIndexChanged
I can also sort the listview.

How can I set the bindingmanager.position in the selectindexchanged event too the right record-index in my dataset?

After sorting, the index in the listview is not the index of the record in the dataset.

With custom collections, when I add an object I give it an internal id. So, I will always find the right object.
With a dataset I can not give him an internal id, because dataset is filled up with the sqldataadapter.

Thanks

Windows Form TabPage

Jubal15-Oct-03 4:19

Jubal

15-Oct-03 4:19

I have a windows form with two tabpages. On the form load I want to move the second tabpage to the front(or have it display). Any ideas on how to do this? I have tried using tabPage2.focus. Didn't work.

thanks

Jubal

Re: Windows Form TabPage

Wjousts15-Oct-03 5:49

Wjousts

15-Oct-03 5:49

Have you tried:

<br />
MyTabControl.SelectedTab = tabPage2;<br />

I think that works....

Using C# in MFC Project

Anonymous14-Oct-03 23:53

Anonymous

14-Oct-03 23:53

How to Active C# form in MFC project?

Versioning Solution

Member 37818914-Oct-03 20:55

Member 378189

14-Oct-03 20:55

Hi,

Is that possible to version a solution ?? If yes please help me out.

We have 2 phases in our web application project. Now the 1st phase is over. 2nd phase is coming now. Now, the question is how I maintain 1st phase changes in the solution. Can I version the phase 1 solution ?
Client is using phase 1 solution now. So any changes if they say we shd be in posn to incorporate not any phase 2 requirement.

Please let me know how I go about this. I have an idea of maintaining two different solution in the VSS. But is that possible to have strong name and version it ?

There are ASPX file also can I version it that also ??

Regards

Srinath

Douglas Troy15-Oct-03 6:26

15-Oct-03 6:26

I'm not certain I'll have the exact answer you're looking for, but I'll mention a few things here (also not entirely certain I know what it is you are looking to achieve) ...

If you're using VSS, lock your code down and branch the solution/project. You'll then have a version 1.x.x.x branch and a version 2.x.x.x branch; course, you have to name them yourself.

In the application AssemblyInfo.cs file, you can specify the AssemblyVersion there. By default, it's specified as version ("1.0.*"), and the compiler automatically increments the minor build numbers. Once you've branched your code out, change that to ("2.0.*"); and so on ...

Also, you can create an AssemblyKey file that's different for each release. This is also contained in the AssemblyInfo.cs file that's part of your main solution.

Perhaps if you explained what it is you want to have happen, or not have happen, I could better point in the correct direction(?) ... maybe.

Hope some of that information helped ... Confused | :confused:

Heath Stewart15-Oct-03 11:59

Heath Stewart

15-Oct-03 11:59

Why should he use a different key pair for each release? This, in effect, identifies you as the company. Maintaining version bindings between releases is done using the <runtime> section of the .config file, or using a publisher policy assembly installed in the GAC.

I mean, I agree with the rest of the stuff, I just don't get the latest direction.

It's sort of like Authenticode; you buy an X.509 certification with the right extensions and sign your code with it. It identifies your company - much like assembly key pairs, except X.509 can be traced by easily to the source.

Douglas Troy16-Oct-03 4:44

16-Oct-03 4:44

Heath,

Yes, this was my mistake and failure to properly explain Strong Name Key signing, thank you for pointing out this error. In hind sight, I'm not certain what I was trying to communicate regarding signing of his assembly ... it appears he's provided more information, so I'll have to review that before more information can be provided.

Thanks again for pointing this out,

D.

15-Oct-03 19:38

Douglas,

Thanks for the solution.

Let me explain you my requirement more elaborately.

I have a solution which contains 4 projects. Now we need to freeze the current version(say i freeze to ver 1.0.0.1). There might be some requirement changes with respect to ver 1.0.0.1.

Now there are set of new requirements coming up for the same solution. I dont want to touch prev version, I want to create a new version. Which can hold the new changes.

So changes /bug fixes with respect to ver 1.0.0.1 should not tamper ver 1.0.0.2 (my second ver 2)

Client shd be able to see changes w.r.t ver 1.0.0.1 after all they are god to us. Smile | :)

hope you got my problem

So please Smile | :)

help me

Regards

Srinath

Member 37818915-Oct-03 23:20

Member 378189

15-Oct-03 23:20

Hi Douglas,

Even if I version it, suppose I make changes in version 1, Can I replicate the same in version 2 during the release. Since version 1 goes for some changes I need to have those changes in version 2 only during the final release.

hope you got it. hope I am not bugging you Smile | :)

Regards

Sri

Douglas Troy16-Oct-03 4:58