Example 1.

/// <summary>
/// Returns current UTC time
/// </summary>
/// <returns></returns>
public static DateTime GetCurrentTimeUtc()
{
       DateTime dt = DateTime.UtcNow;
       return dt;
}

Example 2.

bool value;
if(value.ToString.Length() == 4)
  return true;
else if(value.ToString.Length() == 5)
  return false;

else
  return !true && !false;

Example 3.

private void UpdateLabel(string str)
{
   if (str == "!0123clear3210!")
   {
       textBox1.Clear();
       return;
   }
   textBox1.AppendText(str);
}

Example 4.

if ((armid == "3504000036") || (armid == "3504000034"))
{
    if (armid == "3504000036")
    {
       PlaceSave = "3243100001";
    }
    if (armid == "3504000034")
    {
       PlaceSave = "2311030001";
    }
}

Example 5.

void delete_ServerClick(object sender, ImageClickEventArgs e)
{
  Parent.FindControl(ID).Visible = false;
}

Example 6.

int a=0;
if (a != 0)
{
 a=0;
}
else a=0;

Example 7.

bool exitstatus = true;
if (!extremalexit) { exitstatus = true; }

Example 8.

if (a == null == false) {
}

Example 9.

try
{
    ...
    if (obj == null)
    {
        LogManager.GetLogger("Log").Warn(msg);
        throw new SoapException("Object not found", SoapException.ServerFaultCode);
    }
}
catch (Exception ex)
{
    LogManager.GetLogger("Log").Error(msg, ex);
    throw new SoapException("Object not found, SoapException.ServerFaultCode, ex);
}

Example 10.

protected string TryToUpper(string text)
{
      StringBuilder sb = new StringBuilder();
      foreach(char t in text)
      {
      	try
            {
            	sb.Append(t.ToString().ToUpper());
            }
            catch
            {
            	sb.Append(t.ToString());
            }
      }
      return sb.ToString();
}

1. If you want to exit you app without calling any finalizers or finally blocks use:

Environment.FailFast();

2. Instead of

sting filePath = directoryPath + “\” + filename;

you can use:

sting filePath = System.IO.Path.Combine(directoryPath, filename);

3. Forget about “rn” for new line, you can use Environment.NewLine instead. It’s better because it’s system independent

4. You can create a typed reference from a variable:

int i = 100;

TypedReference typeRef = __makeref(i);

5. From the example above, you can extract the original type:

Type type = __reftype(typeRef);

6. You can extract the value from TypedReference:

int j = __refvalue(typeRef, int);

7. You can use the ‘@’ character in the beginning of variable names. It’s suitable to be used for vars:

var @obj = new object();

8. If you want the garbage collector to collect some object while it can be accessed by the application, you can use the System.WeakReference class, you can read more about it HERE.

P.S. I’ve test all the examples above under .NET Frawork 3.5.

You can use both declarations, they has same meaning and there is no recommendation which one should be used:

public static function myStaticMethod()

or

static public function myStaticMethod()

But in my practice I didn’t see static public declaration. Also, I simple research shows that most of the programmers prefer to put the visibility first. It is better because shows which method can be used. It seems that the better programming practice is to declare public static.

1. Instead of

using (Font f1 = new Font(“Arial”, 10.0f))
{
using (Font f2 = new Font(“Calibri”, 10.0f))
{
//t use f1 and f2 here
}

}

it can be written:

using (Font f1 = new Font(“Arial”, 10.0f), Font f2 = new Font(“Calibri”, 10.0f))
{
//t use f1 and f2 here
}

2. Instead of

bool NameExists(string name) {

return name == “dev” || name == “the” || name == “web” ||

name == “.net”;

}

it can be written:

bool NameExists(string name){

return new[] { “dev”, “the”, “web”, “.net” }.Contains(name);

}

3. You can compare strings ignoring cases in this way str1.ToUpper() == str2.ToUpper(), but it makes additional string allocation, better way is to use OrdinalIgnoreCase: str1.Equals(str2, StringComparison.OrdinalIgnoreCase)

4. The ?? operator can be chained in a bunch of null comparisons:

string result = var1 ?? var2 ?? var3 ?? String.Empty;

5. In the following statement: SomeClass obj = (SomeClass) obj;  If obj is not SomeClass, a class cast exception will be thrown, if you want to return null if obj is not SomeClass, you can use the as operator: SomeClass obj = obj as SameClass;

6. I don’t thinks it’s recommended, but you can use Unicode characters in names, ex.

public string ТихомирIvanov()

{

return “My name is Tihomir Ivanov”;

}

But more interesting is that you can also use Unicode escapes, ex.

public string Tu0418хомирIvanov ()

{

return “My name is Tihomir Ivanov”;

}

7. In C# you can create JavaScript-like anonymous inline functions, ex.

var var1 = new Func<String>(() =>

{

return “DevTheWeb.NET”;

})();

8. Let’s we have the following  generic method declaration:

public void Func<T>(T value);

We can call it in this way: Func<int>(1);

But we can also in this way:

Func(5);
Note: The second way of calling a generic method won’t work if we’re calling the method through reflection.

That’s all. I hope you’ve found something useful in the examples above. Next Thursday, I’ll add new post about interesting things in C#.

I think if the enum will be used by a single class then you should add the enum declaration inside the class. But if the enum is global and will be used by many classes you can create a new file where you can add declarations of all globally used enums. But to create separate files for all enums it too wasteful

using System.Collections.Generic;

…

public static Dictionary<string, string> dict = new Dictionary<string, string>() {
{“key 1″, “value 1″},
{“key 2″, “value 2″},
{“key 3″, “value 3″}
};

That’s all. It’s similar to the array declaration

byte[] string2byteArr = System.Text.UnicodeEncoding.GetBytes(“Some String”);

2. Lazy load something

rather than

Foo foo;
public Foo Foo
{
get
{
if (foo == null)
{
foo = new Foo();
}
return foo;
}
}

you can try:

Foo foo;
public Foo Foo
{
get { return foo ?? (foo = new Foo()); }
}

3. Converting single char to string

char myChar = ‘A’;

rather than

string myString = new string(char [] { mychar });

you can try:

string myString = mychar.toString();

4. String literals can span multiple lines:

string s = @”First Line
Second Line
Last Line”;

5. Object initializers
rather than

public class Foo
{
public string Bar { get; set; }
}

for (int i = 0; i < 100; i++)
{
Foo foo = new Foo();
foo.Bar = “Hello World”;
myList.Add(foo);
}

instead of

for (int i = 0; i < 100; i++)
myList.Add(new Foo { Bar = “Hello World” });

6. Using the ‘default’ keyword in generic types:

T t = default(T);

results in a ‘null’ if T is a reference type, and 0 if it is an int, false if it is a boolean, etc.

7.  If you want to exit your program without calling any finally blocks or finalizers use:

Environment.FailFast()

8. Compare strings ignoring cases instead of using ToLower method:

“Some String”.Equals(“string STRING”, StringComparison.InvariantCultureIgnoreCase);

9. Regular expressions and file paths:

“c:\program files\oldway”
@”c:program filenewway”

10.  Implicit generic parameters on functions:

public void Something<T>(T value);

Instead of

Something<int>(5);

You can:

Something(5);

1.Using String variables:

if (someString.Length > 0)
{
// …
}

… but someString could be a null:

if  (!String.IsNullOrEmpty(someString))
{
// much better now !?
}

2.String concatenation

string s = “dev”;
s += “-”;
s += “the”;
s += “-”;
s += “web”;
s += “.”;
s += “com”;

This is not very effective and the program will work slower instead of using StringBuilder class and it’s Append method:

StringBuilder sb = new StringBuilder();
sb.Append(“dev”);
sb.Append(“-”);
sb.Append(“the”);
sb.Append(“-”);
sb.Append(“web”);
sb.Append(“.”);
sb.Append(“com”);
3.Using Console

Console.WriteLine(“A= ” + 1 + ” B=” + 2 + ” C= ” + someValue);

same as 2. it’s not very effective. What about this:

Console.WriteLine(“A: {0}nB: {1}nC: {2}”, 1, 2, someValue);

4.Parse Integer value from string variable

int i = int.Parse(Request.QueryString["id"]);

but if we’ve a url like this yourpage.aspx?id=A6 the above method will throw an exception. What about TryParse method?

int i;
if (!int.TryParse(Request.QueryString["id"] , out i))
{
//…
}

5. Calling IDbConnection’s Close method

IDbConnection dbConn = null;

try
{
dbConn = new SqlConnection(“some Connection String”);
dbConn.Open();
}
finally
{
dbConn.Close();
}

Calling SqlConnection’ constructor may throw an Exception, should we call Close method then !?

IDbConnection dbConn = null;

try
{
dbConn = new SqlConnection(“Some Connection String”);
dbConn.Open();
}
finally
{
if (dbConn != null)
{
dbConn.Close();
}
}

6.Using List class

public void SomeMethod(List<SomeItem> items)
{
foreach(var item in items)
{
// do something with the item…
}
}

If we just loop through the List of items. In this case, requiring a list is an over specification, so it could done in this way:

public void SomeMethod(IEnumerable<SomeItem> items)
{
foreach(var item in items)
{
// do something with the item…
}
}

7.Use numbers in more that simple numbers way

if(mode == 1) { … }
else if(mode == 2) { … }
else if(mode == 3) { … }

Why don’t we use Enumerations in this case:

public enum SomeEnumerator
{
DefaultMode = 1,
SafeMode = 2,
NormalMode = 3
}

if(mode == SomeEnumerator.DefaultMode) { … }
else if(mode == SomeEnumerator.SafeMode) { … }
else if(mode == SomeEnumerator.NormalMode) { … }

8.String Replace

string s = “www.DevTheWeb.NET is a cool site”;
s.Replace(“cool”, “awful”);

Nothing changed in s’ value, it’s still “www.DevTheWeb.NET is a cool site”

s = s.Replace(“cool”, “awful”);

Now s’ value is realy changed.

I hope you’ll like the list of common C# mistakes

P.S. If you know some cool C# mistake, please, post a comment about it