Reading and writing data (securely) in a C# 2.0 Win App

1. Add a reference to System.Configuration.dll

2. Add using System.Configuration;

3. Use the following code:

Configuration c = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
c.ConnectionStrings.ConnectionStrings.Add( new ConnectionStringSettings("conn 1", "Server=local; Database=Test; Password=myPassword; User Id=myUser;"));

ConfigurationSection section = c.GetSection("connectionStrings");
if (section != null)
{
if (!section.IsReadOnly())
{
section.SectionInformation.ProtectSection("RsaProtectedConfigurationProvider");
}
}
c.Save();

Call one constructor from another

Avoid duplicating code...

class C1
{
public C1() { }
public C1(string s):this() { }
}

Defining a generic method in a non-generic class

For instance:


class Class2
{
public static void GenericMethod <X>(int n)
where X:new()
{
X myXinstance = new X();
}
}

The method can be called like this:
Class2.GenericMethod <System.Collections.ArrayList> (100);

Getting the identity of an assembly

Use the following code to create an identity object for an assembly. It can be used when passing it to the GetStore method when trying to one an isolated file storage (iso) store that requires that the identity of the assembly be provided.


System.Reflection.Assembly a = System.Reflection.Assembly.GetExecutingAssembly();
string assemblyPath = a.FullName;
System.Security.Policy.Url url = new System.Security.Policy.Url(assemblyPath);

Using the new delegate Syste.Predicate

Here's a small case when the new C# 2.0 feature, Predicate<T> may be useful:

Consider an array of file paths retrieved from disk:
string[] s = new string[4] { @"C:\a.jpg", @"C:\b.txt", "c.bmp", "d.swf" };

We can find all the image files (i.e those that have a certain extension) by doing this:

Predicate<string> p = new Predicate<string>(CheckIfImageFile);
string[] newS = Array.FindAll<string>(s, p);

Where CheckIfImageFile is defined here:

static bool CheckIfImageFile(string fullFilePath)
{
string commonImageExtensions = "*.png;*.jpg;*.gif;*.bmp";
if (commonImageExtensions.IndexOf(Path.GetExtension(fullFilePath)) > 0) return true;

return false;
}

Undocumented C# keywords

I found some interesting undocumented keywords (http://www.eggheadcafe.com/articles/20030114.asp):

__makeref, __refvalue, __reftype, __arglist.


Here are a few examples:
int i = 10;
TypedReference tr = __makeref(i);

Type t = __reftype(tr);
int j = __refvalue( tr,int);


protected void Page_Load(Object sender, EventArgs e)
{
int x=85;
string y = "a stringy thingy";
double d=19.45;
WriteToPage(__arglist(x,y,d));
}

public void WriteToPage(__arglist)
{
ArgIterator ai = new ArgIterator(__arglist);
while(ai.GetRemainingCount() >0)
{
TypedReference tr = ai.GetNextArg();
Response.Write(TypedReference.ToObject(tr)+"");
}
}

Debugging Windows Services In Visual Studio 2005

To do that, change the body of the Main method of the Windows service:


#if (!DEBUG)
ServiceBase[] ServicesToRun;
ServicesToRun = new ServiceBase[] { new MyService() };
ServiceBase.Run(ServicesToRun);
#else
MyService service = new MyService();
service.MyOnStart();
#endif

You will get two error messages at the beginning but you can continue debugging.