Acquiring a property value

Blubbo

When a custom control (DeviceMonitor) was generated along with the property as follow:

public bool isConnected {get; set;}

then in the main form to add the control to the form...

DeviceMonitor devMon = new DeviceMonitor();
Control deviceControl= devMon;
this.Controls.Add(deviceControl);

Somewhere in the code, I would need to acquire the "isConnected". I tried

if (deviceControl.IsConnected)
{
...
}

but the .net doesn't see the property value of "isConnected". How do I get this property value this way? Should I use this instead in the main form:

DeviceMonitor devMon = new DeviceMonitor();
this.Controls.Add(devMon);

This way, I can get it as:

if (devMon.IsConnected)
{
...
}

Any response?

N8tiv

I'm just starting to learn this stuff, I'm about halfway through this e-book course… It's just now starting to cover "properties"… Maybe there is something new in the .Net that allows properties on a Boolean? As far as I know, Boolean is only true or false. I forgot what the default value is a Boolean… I'm more guessing than giving you an answer because I'm still learning C# myself. Get rid of the: get; set And replace that with: true Then you can make a call to your Boolean "isConnected"… Hopefully someone will correct me if I'm wrong. Good luck

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Brisingr Aerowing

C# is case sensitive. So isConnected != IsConnected

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Dave Kreskowiak

You defined deviceControl as Control, which, if oyu look at the documentation for Control, doesn't have a IsConnected property. You have to use the code you listed second, under "should I use this instead". I suggest picking up a beginners book on C# and working through it. This is a very basic concept you're going to have to learn completely before building on it.

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N8tiv

So, where does my answer fit in? I'm halfway through a book I picked up at 'brainmeasures dot com'...

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PIEBALDconsult

Do you need to cast it?

Dave Kreskowiak

Truthfully? Not even close. Sorry, but you've got some more work to do.

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Lost User

WidmarkRob wrote:

I'm more guessing than giving you an answer because I'm still learning C# myself.

True.

WidmarkRob wrote:

Get rid of the: get; set

And replace that with: true

Completely wrong, I'm afraid. OP has coded the property correctly, but has not instantiated the object properly.

Use the best guess

OriginalGriff

Just to add to the other responses: Your DeviceMonitor is a UserControl, which means that it is derived from Control (it has to be, otherwise it can't be displayed - even Form is derived from Control via a couple of other classes). That means it inherits (and you can access) all the properties of a Control in your class. But it doesn't work the other way...

DeviceMonitor devMon = new DeviceMonitor();
Control deviceControl= devMon;
this.Controls.Add(deviceControl);

devMon contains a reference to your DeviceMonitor instance, so you can access all the properties and methods of the DeviceMonitor class via devMon:

if (devMon.isConnected)
{
...
}

But deviceControl is a Control reference: it can contain a Control instance, or an instance of any class which is derived from Control, but it can only access the properties and methods of the Control class because that is the only class type it can guarantee that deviceControl contains. It is perfectly legal and correct to say:

DeviceMonitor devMon = new DeviceMonitor();
Control deviceControl= devMon;
this.Controls.Add(deviceControl);
deviceControl = new TextBox();

So the compiler will not let you access a derived class property or method via the base class variable. It's a bit like cars: a Car has four wheels and an engine, but a Ford Fiesta also has Cruise Control, which a Ford Model T doesn't. If you declare a variable as a Car, then you can't access myCar.CruiseControl because the Car may be a Model T. BTW: You don't need to use the deviceControl in your code - you can use a derived class anywhere you can use the base class. So this will work as well:

DeviceMonitor devMon = new DeviceMonitor();
this.Controls.Add(devMon);

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Blubbo

uhh that's not it. Keep on learning! There's so much to learn!

Blubbo

I don't understand your question

Blubbo

I have been programming in C# for a long time. My engineer has programmed this way on the 1st option. I'm trying to figure out and need to revise the code to work with USB device. I've came up with the solution with loss/recovery of the USB device with WndProc process.

Blubbo

Tried to cast the control. Still nothing.

Blubbo

I would have to agree with the 2nd option.

Dave Kreskowiak

I have been programming in C# for a long time. Then why did you ask this question? If what you said is true, this should have been obvious to you.

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Dave Kreskowiak

Dave Kreskowiak

You have to cast it to the type that contains the property your trying to use, not the one that doesn't.

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Blubbo

I appear to have finally got what I wanted... after googling, I ran into this site... http://stackoverflow.com/questions/987982/how-can-i-get-the-value-of-a-string-property-via-reflection[^] and kept option 1... I modified the code in Main form and it got the value I was looking for. In this example, it would go as:

bool bResult = (bool)devMon.GetType().GetProperty("isConnected").GetValue(devMon, null);

PIEBALDconsult

Quite a performance hit if you do that a lot.

Lost User

And what happens if that object does not have a property named isConnected? You have received some good advice here from people who are trying to help you, so why implement a bad answer from somewhere else?

Use the best guess

coolcat227

Heres one way:

DeviceMonitor devMon = new DeviceMonitor();
Control deviceControl= devMon;
this.Controls.Add(deviceControl);

...

if((deviceControl as DeviceMonitor).isConnected)
{
...
}

a better way:

DeviceMonitor devMon = new DeviceMonitor();
this.Controls.Add(devMon);

...

if (devMon.isConnected)
{
...
}