C++ -> C# need help with: ** (pointer to a pointer?) - C# Discussion Boards

Re: C++ -> C# need help with: ** (pointer to a pointer?)

25-Apr-04 4:34

I should've read this message first.

Since CreateSession is a COM object method, you should just instead create a COM interop assembly, a.k.a. a RCW (Runtime Callable Wrapper). In VS.NET, just right-click on your project and select Add Reference. Click the COM tab and find the typelib. Double-click it to add it to the list and click OK. An interop assembly is created with all the interfaces, enums, parameters, etc. defined. All you have to do is use them and make sure that the interop assembly (it will get copied to your build directory) gets deployed as well with your library or application).

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Heath Stewart25-Apr-04 4:31

25-Apr-04 4:31

If this is a method on a COM object, then you should create an interop assembly using tlbimp.exe, or add a COM reference to your project in VS.NET which does the same thing.

If this is a function exported by a DLL, you can use the following signature:

[DllImport("whatever.dll", PreserveSig=true)]
private static extern int CreateSession(ref IMediaStatusSession MediaStatusSession);

IMediaStatusSession would be an interface that you would have declare that matches the native interface using the same order of methods (if inheritted from IUnknown or dual), dispatch IDs (if inheritted from IDispatch or dual), and signatures; or that is declared in an interop assembly created from the typelib.

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ArrayList Indexing: Help

24-Apr-04 13:59

Hi,

I have an array list with elements.
I am unable to access them through indexing.
Here ia my code:

int index = itemList.Count; Where "itemList" is my "ArrayList".

for (int i=0; i < index; i++)
{
string local = (string)itemList[i];
Console.WriteLine("Printing Array: {0} and I:{1}",(string)itemList[i], i);
}
My "local" string first gets assigned zero th element of "ArrayList", but when i=1,2,3,4 etc. my "local" string still has zero th element only.
I cannot use indexing this way. I have to use "MoveNext()" of Enumerator class to access?

Thanks & Regards,
Raj

Colin Angus Mackay24-Apr-04 14:22

Colin Angus Mackay

24-Apr-04 14:22

Your code is not very readable - the < symbols have been interpreted as the start of HTML tags.

Please replace the < symbols with < so that when it is posted it will display correctly.

Thanks.

"You can have everything in life you want if you will just help enough other people get what they want." --Zig Ziglar

Coming soon: The Second EuroCPian Event

24-Apr-04 16:35

Hi Sorry for messing up in Copy/paste.
Here is the code again.

int index = itemList.Count; Where "itemList" is my "ArrayList".

for (int i=0; i < index; i++)
{
string local = (string)itemList[i];
Console.WriteLine("Printing Array: {0} and I:{1}",(string)itemList[i], i);
}

Again my problem is

If there are 10 elements I am getting first element printed 10 times.
But If I use

System.Collections.IEnumerator myEnumerator = myCollection.GetEnumerator();
while ( myEnumerator.MoveNext() )
Console.Write( "\n{0}", myEnumerator.Current );

I am getting the correct output.

Thanks & Regards,
Raj

Colin Angus Mackay24-Apr-04 14:25

Colin Angus Mackay

24-Apr-04 14:25

Out of curiousity. If all your elements are strings, why not use the System.Collections.Specialized.StringCollection class instead?

"You can have everything in life you want if you will just help enough other people get what they want." --Zig Ziglar

Coming soon: The Second EuroCPian Event

Jon G24-Apr-04 14:36

Jon G

24-Apr-04 14:36

Hey, try this:

ArrayList itemList = new ArrayList();<br />
itemList.Add("string goes here");       //it can be any object type

Then, you can access them like this:

for (int i=0; i < itemList.Count; i++)<br />
{<br />
    Console.WriteLine("Printing Array: {0} and I:{1}", (string)itemList[i], i.ToString() );<br />
}

Member 95766524-Apr-04 16:31

Member 957665

24-Apr-04 16:31

I tried that. Only first element (string)itemList[0] is getting printed. Suppose if count is 10, first element is getting printed 10 times.

If I use

System.Collections.IEnumerator myEnumerator = itemList.GetEnumerator();
while ( myEnumerator.MoveNext() )
{
Console.Write( "\n{0}", myEnumerator.Current );
}

I am getting correct output.

Thanks & Regards,
Raj

Member 95766524-Apr-04 17:42

Member 957665

24-Apr-04 17:42

I got it.

Thnaks
Raj

Colin Angus Mackay25-Apr-04 1:22

Colin Angus Mackay

25-Apr-04 1:22

You know that if a object supports the IEnumerable interface (which provides the GetEnumerator() method) that you can use it in a foreach loop?

Here is an article about Using IEnumerator and IEnumerable in the .NET Framework[^]

"You can have everything in life you want if you will just help enough other people get what they want." --Zig Ziglar

Coming soon: The Second EuroCPian Event

Adding a CheckBox column in DataGrid

Jeff Varszegi25-Apr-04 7:05

Jeff Varszegi

25-Apr-04 7:05

I suspect that you're getting confused somewhere along the line. Paste the exact code below into your project, run it, and report back:

<br />
			ArrayList itemList = new ArrayList();<br />
			<br />
			itemList.Add("0");<br />
			itemList.Add("1");<br />
			itemList.Add("2");<br />
			itemList.Add("3");<br />
			itemList.Add("4");<br />
			itemList.Add("5");<br />
			itemList.Add("6");<br />
			itemList.Add("7");<br />
			itemList.Add("8");<br />
			itemList.Add("9");<br />
			<br />
			int count = itemList.Count;<br />
			for (int i=0; i < count; i++) {<br />
				Console.WriteLine("Printing Array: {0} and I:{1}", itemList[i], i);<br />
			} <br />

You're probably confused about assigning int variables. I imagine that you take a read of the Count property before you fill the ArrayList, yes? Well, that object is assigned by value, not by reference, because int is a value type. The part where you populate the array is the only piece missing in the information you gave us; notice the ensuing confusion? Next time, I'd include all the code that's probably part of the problem. I'm not being crusty, just trying to give helpful advice. Anyway, notice that above I read Count after filling the data. This is better on performance than reading Count every trip through the loop.

ArrayList is built specifically to replicate the semantics of accessing an array by index, and it uses an array internally to hold its data. It's probably silly to use an enumerator in your case. Enumerators were made so that all lists can be considered just to be implementations of IList.

Your explicit casts are unnecessary, but I left them in.

Regards,

Jeff Varszegi

Jon G24-Apr-04 13:41

Jon G

24-Apr-04 13:41

How would you add a CheckBox column in a DataGrid?

Any help on this topic will be appreciated. Thanks in advance,
Jon

Heath Stewart25-Apr-04 4:26

25-Apr-04 4:26

As I mentioned the other day, add a DataGridTableStyle to your DataGrid, which would have either DataGridTextBoxColumns, DataGridBoolColumns, or some custom DataGridColumnStyle. Make sure the DataGridTableStyle.MappingName matches-up with the table name (for data-binding to DataSets or DataTables) or class name (for binding against other IList or IListSource implementations).

Just see the documentation for the DataGridTableStyle in the Platform SDK for more information and an example, as well as the other classes and properties I mentioned above. It's really pretty simple, but you must make sure that your DataGridTableStyle.MappingName is correct or your table style doesn't get used.

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Jon G25-Apr-04 6:58

Jon G

25-Apr-04 6:58

You are a great help with giving me exactly the key words to point me in the right direction. Iv'e created the DataGridBoolColumns style, and made the MappingName match the table column i'm "binding" it to. How do I tell it to display a CheckBox? I don't understand how they add the CheckBox control inside the columns.

Heath Stewart25-Apr-04 7:33

25-Apr-04 7:33

Like I said, you add a DataGridBoolColumn to your table style that you added with it's MappingName set to your boolean column. If you use values other than "True" or "False" for your data, then you need to set the DataGridBoolColumn's TrueValue and FalseValue properties. Just see the DataGridBoolColumn documentation for an example.

Also, try playing around with this in the VS.NET DataGrid designer and then examine the code. It works best if you use a typed DataSet.

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