Category: .NET

Let’s suppose that you have 2 functions = one true sync and one true async . Let’s suppose more that the sync one can must finish before calling next time ( think about some weird COM component or , in our days, SqlConnection )

If we look just at the async function , we could wait for all. However, the sync function must be called sync

One solution is to make different calls:

var list = new List<Task<int>>(nr);
//add async to list

await Task.WhenAll(list)

//call each sync

But I want to make really async – and one solution is lock

We could wrote the sync function in async manner like this:

//SemaphoreSlim sem = new SemaphoreSlim(1);
static object myObject = new object();
async Task<int> syncTask(int i)         {             
lock (myObject)             
//try{                 
//await sem.WaitAsync();                                 
CallSyncFunction();                             
//}             
//finally             
//{                 
//sem.Release();             
//}                                   
}

The trick that I  used is lock, because the syntax is easier than SemaphoreSlim (BTW: if you want to learn about threading, jump directly to http://www.albahari.com/threading/)
In this manner, the sync function is modified in async -and, more, it waits for completion before entering the second time.

The code is on github on

More details in the Wiki https://github.com/ignatandrei/AsyncSyncLock/wiki or in the code https://github.com/ignatandrei/AsyncSyncLock/

Please spot the errors in the following code in VB.NET:

Dim Diff As String = con.ExecuteCommand(“SELECT DATEDIFF(Day, (select [date] from table where Username = ‘” + txtUserName.Text + “‘), ‘” & DateTime.Now.ToString() & “‘)”)
If (Diff > 30) Then
Response.Redirect(“PleaseChangeMyPassword.aspx”)
End If

( find at least 3…)

Side note:

No wonder Visual Basic has died ( more or less). Guess future of server javascript ….

A Visual Studio pacakge is a plugin of Visual Studio that can do (almost) anything inside Visual Studio

I have made a small project that generates a list of all solution ( or project) references from VS:

            foreach (var project in dte.Solution.Projects)
            {
                var p = project as Project;
                if (p == null)
                {
                    continue;
                }

                var vsproject = p.Object as VSLangProj.VSProject;
                if (vsproject == null)
                    continue;

                string nameProject = p.Name;
                foreach (var reference in vsproject.References)
                {
                    var r = reference as Reference;
                    if (r == null)
                        continue;

                    var pathRef = r.Path;

                    //this is a package                    
                    var pa = new PackageAdd();
                  
                    pa.ProjectName = p.Name;
                    pa.IdentifierPackage = r.Identity;
                    pa.VersionPackage = r.Version;
                    pa.NamePackage = r.Name;

                  



                    if (r.SourceProject != null)
                    {
                        
                        pa.NamePackage = r.SourceProject.Name;
                    }
                    sb.AppendLine(pa.ToString());
                }
            }

You can find the solution at https://github.com/ignatandrei/ToolsAndUtilities/tree/master/VS2015/FindReferencesVS

Also the video is at https://youtu.be/a3YHVjJ9fm4

Enjoy!

In our days it is simpler to make an application by putting together some API . I wanted to make a list of all my 5 Minutes .NET playlist videos . First, I have tried to find an application(nothing). Then I have read  You Tube API from https://console.developers.google.com/apis/library . With 2 http requests( one for retrieving all videos from a playlist, the other to find video details) and a NuGet package to export to Excel/Word/PDF/HTML it was simple. You can find the whole project at https://github.com/ignatandrei/YouTube . A video demo at https://www.youtube.com/watch?v=wNHDsHtLBq4 . And the whole list at https://github.com/ignatandrei/ToolsAndUtilities/tree/gh-pages

If you have worked with COM, you know that for every COM object that you access is not only necessary to null the reference, but also call Marshall.ReleaseCOMObject .

This is a very error prone task, because you have all try / finally blocks

 
// declare a, ws, w 
try{ 
a=new Application(); 
ws = a.Workbooks; 
w = ws.Add(); 
//code 
}
 catch(...) {
 if( w != null){ 
Marshal.ReleaseComObject(w); 
w = null; 
}
 if(ws !=null){ 
Marshal.ReleaseComObject(ws); 
ws = null; 
} 
if( a!= null) { 
Marshal.ReleaseComObject(a); a= null; 
} 
} 

All of this could be done easy with IDisposable, if

1. IDisposable calls the Marshal.ReleaseCOMObject

2. Find a way to call methods / properties on the COM object from the class that implements IDisposable

I have done this and the result is like this:

 
using (dynamic a = new ComDisposable(new Application())) { 
using (dynamic ws = a.Workbooks) { 
using (dynamic w = ws.Add()) { 
using (var shs = w.Sheets) { 
using (var s = shs[1]) { 
//Worksheet a; 
using (var r = a.Range("A1")) { 
r.Value2 = "http://ignatandrei.github.io/ToolsAndUtilities/";; 
using (var f = r.Font) { 
f.Bold = true; 
}
 }
 }
 }
 w.SaveAs(fileName); 
w.Close(); 
} 
}
 a.Quit(); } 

Video at https://youtu.be/2qbAcSjL1gU

NuGet package at https://www.nuget.org/packages/ReleaseComObjectDisposable/

AppContext is like Application in ASP.NET (MVC). You can see the value all over the application

AppContext.SetSwitch("OCR", true);

And we can have the result in all dll’s by

 public bool IsOCREnabled()
        {
            bool test;
            if (!AppContext.TryGetSwitch("OCR", out test))
                return false;

            return test;
        }

Video demo at https://youtu.be/GMgn4o3yPqw

For many programmers a try/catch with stack trace it is enough

try
{
var p = new Person();
p.DateOfBirth = DateTime.Now.AddYears(-10);
p.Drink(10, 2);
}
catch (Exception ex)
{
Console.WriteLine("ERROR OCCURED " + ex.StackTrace);
}

Others want to see also functions arguments, like in

p.Drink(10, 2);

will produce the result

ERROR An exception occured in method InstrumentationPostSharp.Person.Drink with (beersNumber = 10 , vodkaNumber = 2)

For this you can install the package
https://www.nuget.org/packages/LoggerAspect.Nlog

that have full source code at
https://github.com/vnvizitiu/AOP/tree/master/PostSharpTutorial

and watch my video for more details
https://youtu.be/qe2kpuuWXkw

When you intercept exceptions( for logging ) you can

 
catch (Exception ex)
            {
                //TODO: log : 
                //https://youtu.be/OvzcBTm3Sow
                string s = ex.Message;
                throw ex;
            }
 

or

 
catch (Exception ex)
            {
                //TODO: log : 
                //https://youtu.be/OvzcBTm3Sow
                string s = ex.Message;
                throw ;
            }

The difference is small – but the consequences are losing the original stack trace , if you

 throw ex; 

I have done a small video about this : https://youtu.be/Deigld3Bqko

I have not covered ExceptionDispatchInfo  that you can see an usage here: http://blogs.microsoft.co.il/sasha/2011/10/19/capture-transfer-and-rethrow-exceptions-with-exceptiondispatchinfo-net-45/