Monday, October 11, 2010

List of processes running on Remote/Local Computer using C#

ArrayList alist = new ArrayList();

// From remote machine
Process[] processes = Process.GetProcesses("RemoteComputerName"); 

// From local machine
Process[] processes = Process.GetProcesses();    

foreach (Process process in processes)
{
       alist.Add(process.ProcessName);
}

Friday, October 8, 2010

Limitations of COM Interop

Following is the list of some shortcomings:

  • Static/shared members: COM objects are fundamentally different from .Net types. One of the differences is lack of support for static/shared members.
  • Parameterized Constructors: COM types don't allow parameters to be passed into a constructor. This limits the control you have over initialization and the use of overloaded constructors.
  • Inheritance: One of the biggest issues is the limitations COM objects place on the inheritance chain. Members that shadow members in a base class aren't recognizable, and therefore, aren't callable or usable in real sense.
  • Portability: Operating Systems other than Windows don't have registry. Reliance on Windows registry limits the number of environments a .Net application can be ported to.

Why Visual Studio hangs

Every once in a while, VS seems to take forever to display a screen to the point that it seems to hang. Most of the time, it hangs, while accessing Fonts and Colors page in Tools/Options dialog. The issue is not that there is some weird code that executes very slowly. It happens that this page is implemented using .NET components. Now the majority of VS is built with native code and during most of its execution,, the CLR is never loaded. However, when the user accesses one of these features, the CLR must be loaded, before we can begin executing the relevant IL. It is this process that is time-consuming and annoying to the user. There are two problems for the users here: first, there is no feedback during loading of the CLR; second: the problem can occur multiple times within a single session of VS.


I am trying to figure out the reason for this second issue. Let me know, if any of you knows.

Optional Parameter issue with COM and C#/VB

As we all know, C# doesn't support optional parameters(till framework 3.5) whereas VB does.In the same way, COM components don't support parameter overloading, so for each value in a parameter list, we've got to pass in something, even if it does nothing. Moreover, COM parameters are always passes by reference, which means we can't pass NULL as a value.


In VB 2005, this is not really as issue because it supports optional parameters and we can just leave them out. But C# doesn't support this, so one have to create object variables and pass them in.


See following code sample:
using Microsoft.Office.Core;
using Microsoft.Office.Interop.Excel;  // Must have office installed
Application NewExcelApp = new Application;
NewExcelApp.Worksheets.Add();       // This will not compile


So, as a workaround, the Type.Missing field can be used and this field can be passed in with the C# code and the application will work as expected. 


Check it in below code snippet:


using Microsoft.Office.Core;
using Microsoft.Office.Interop.Excel;  // Must have office installed
private Object OptionalParamHandler = Type.Missing;
Application NewExcelApp = new Application;
NewExcelApp.Worksheets.Add(OptionalParamHandler ,OptionalParamHandler ,OptionalParamHandler ,OptionalParamHandler ); 

This approach allows your code to work in C# :)