LINQ tip – Ordering collection using existing array/collection using OrderBy

Taswar Bhatti November 29, 2013 5 Comments

Here is a LINQ tip where you may wish to order a collection with an existing ordering of another collection. Example:

int[] displaySeq = new int[] { 1, 8, 5, 7, 13 }; //the ordering we want at the end

//collection that we will be sorting on
List<Person> people = new List<Person>();
people.Add(new Person { DisplaySeq = 5});
people.Add(new Person { DisplaySeq = 13});
people.Add(new Person { DisplaySeq = 7});
people.Add(new Person { DisplaySeq = 1});
people.Add(new Person { DisplaySeq = 8});

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int[] displaySeq = new int[] { 1, 8, 5, 7, 13 }; //the ordering we want at the end

//collection that we will be sorting on

List<Person> people = new List<Person>();

people.Add(new Person { DisplaySeq = 5});

people.Add(new Person { DisplaySeq = 13});

people.Add(new Person { DisplaySeq = 7});

people.Add(new Person { DisplaySeq = 1});

people.Add(new Person { DisplaySeq = 8});

Currently as it stands our data is stored in the order of { 5, 13, 7, 1, 8 } and we wish to order them in terms of { 1, 8, 5, 7, […]

.NET, C#

.net, C#, csharp, dotnet, LINQ

C# tip – Marking method or class as Obsolete/Deprecated

Taswar Bhatti November 25, 2013 No Comments

Obsolete or Deprecated? How do you mark a class or method as deprecated/obsolete? By using the Obsolete attribute

[Obsolete]
public class Person { }

[Obsolete("Class is obsolete, use PersonImpl")]
public class Person { }

//compilation to fail methods calling this code
[Obsolete("Class is obsolete, use PersonImpl", true)]
public class Person { }

[Obsolete("Method is obsolete, use SomeMethod2", true)]
public void SomeMethod() { }

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[Obsolete]

public class Person { }

[Obsolete("Class is obsolete, use PersonImpl")]

public class Person { }

//compilation to fail methods calling this code

[Obsolete("Class is obsolete, use PersonImpl", true)]

public class Person { }

[Obsolete("Method is obsolete, use SomeMethod2", true)]

public void SomeMethod() { }

.NET, C#

.net, C#, csharp, dotnet

C# Null Coalescing Operator

Taswar Bhatti November 21, 2013 No Comments

The ?? operator is called the null coalescing operator. It is used for providing a default value for Nullable types or reference types. Example:

int? age = null;

//what ?? implies is possiblyNullValue ?? valueIfNull
int myAge = x ?? 100; //if x is not null then assign x else 100

string? person = null;
string? localDefault = null;
string globalDefault = "abc";

string anybody = person ?? localDefault ?? globalDefault; //chaining ??

//lazy loading/populating
private SomeObj _lazyField = null;
public SomeObj MyProperty
{
    get { return _lazyField ?? (_lazyField = new SomeObj()); }
}

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int? age = null;

//what ?? implies is possiblyNullValue ?? valueIfNull

int myAge = x ?? 100; //if x is not null then assign x else 100

string? person = null;

string? localDefault = null;

string globalDefault = "abc";

string anybody = person ?? localDefault ?? globalDefault; //chaining ??

//lazy loading/populating

private SomeObj _lazyField = null;

public SomeObj MyProperty

{

get { return _lazyField ?? (_lazyField = new SomeObj()); }

}

One of the disadvantage of ?? is it can create code that is not that readable. e.g a ?? b ?? c ?? d ?? e

.NET, C#, Uncategorized

.net, C#, csharp, dotnet

C# tip property with different accessibility scopes

Taswar Bhatti November 20, 2013 No Comments

In C# you can have property with different scope (property accessors). Properties in C# can be marked as public, private, protected, internal, or protected internal. Example:

public int MyProperty { get; private set; }
public string Name { get; protected set;}
public int Age { get { return _age; } } // no set but still valid
private string Fullname { get; set; } //both are private only class can access it
internal string LName { get; set; } //only code in same assembly can access
protected internal string FName { get; set; } //only code that inherit and in same assembly
virtual string PersonName { get; set; } //use override keyword in derived class
static int Count { get; set; } // avaiable to caller at any time

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public int MyProperty { get; private set; }

public string Name { get; protected set;}

public int Age { get { return _age; } } // no set but still valid

private string Fullname { get; set; } //both are private only class can access it

internal string LName { get; set; } //only code in same assembly can access

protected internal string FName { get; set; } //only code that inherit and in same assembly

virtual string PersonName { get; set; } //use override keyword in derived class

static int Count { get; set; } // avaiable to caller at any time

.NET, C#

.net, C#, csharp, dotnet

C# optional parameters

Taswar Bhatti November 18, 2013 No Comments

C# 4.0 allows one to use named and optional parameters. Example:

int Calculate(int x = 1, int y = 2)
{
   int someNumber = 0;
   //some algorithm to calculate
    return someNumber * y * x + 5 * 0.5;
}

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int Calculate(int x = 1, int y = 2)

{

int someNumber = 0;

//some algorithm to calculate

return someNumber * y * x + 5 * 0.5;

}

One can call the method in multiple ways

int result = Calculate(1, 2);
int result = Calculate(5); //value for x only, y is default to 2
int result = Calculate(); //value for x is 1 and y is 2
int result = Calculate(x: 123, y: 987); //named argument
int result = Calculate(y: 345 x: 678); //named argument in reverse 
int result = Calculate(x: 123, 456); //compiler error not allowed position argument cannot follow name argument
int result = Calculate(1, y: 456); //name argument can follow position argument

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int result = Calculate(1, 2);

int result = Calculate(5); //value for x only, y is default to 2

int result = Calculate(); //value for x is 1 and y is 2

int result = Calculate(x: 123, y: 987); //named argument

int result = Calculate(y: 345 x: 678); //named argument in reverse

int result = Calculate(x: 123, 456); //compiler error not allowed position argument cannot follow name argument

int result = Calculate(1, y: 456); //name argument can follow position argument

Additional note, one cannot provide a gap in arguments. Example:

int Calculate(int x, int y = 2, int z) //invalid
int Calculate(int x, int y = 1, int z= 5) //valid


int result = Calculate(1, , 3); //invalid
int result = Calculate(1, 8); //z takes the value of 5 as default

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int Calculate(int x, int y = 2, int z) //invalid

int Calculate(int x, int y = 1, int z= 5) //valid

int result = Calculate(1, , 3); //invalid

int result = Calculate(1, 8); //z takes the value of 5 as default

.NET, C#

.net, C#, csharp, dotnet

The using statement in C#

Taswar Bhatti November 14, 2013 No Comments

The using statement in C# is a form of shortcut for try and finally block of code. Things to note is in order to use the using statement the object needs to implement the IDisposable interface, and using does not catch Exception, it just guarantees the call of Dispose. Example:

try {    
  connection = new SqlConnection("");
}
finally {
  if(connection != null)
     connection.Close();
}

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try {

connection = new SqlConnection("");

}

finally {

if(connection != null)

connection.Close();

}

Can be replaced with […]

.NET, C#

.net, C#, csharp, dotnet

I refuse to answer your stupid singleton question in interview

Taswar Bhatti November 13, 2013 No Comments

In interviews there is always the Singleton question, I personally refuse to answer it on interview. The reason is very simple I don’t code singletons anymore. I use my IoC Container to provide me with a singleton. Sorry if you dont know what an IoC (Inversion of Control Container) is, then you are still in […]

.NET, C#, Design

.net, C#, csharp, Design Pattern, dotnet

What is the as keyword in C#? When to use it?

Taswar Bhatti November 12, 2013 No Comments

C# has the as keyword, it is mainly used to cast object of one type to another, and if it fails it should return a null rather than crashing the program or throwing exception. From MSDN documentation it states: You can use the as operator to perform certain types of conversions between compatible reference types […]

.NET, C#

.net, C#, csharp, dotnet

C# what is the yield keyword?

Taswar Bhatti November 7, 2013 2 Comments

So C# what is the yield keyword? The yield keyword in C# is basically an iterator, its a form of syntactic sugar added from C# 2.0 to create IEnumerable and IEnumerator objects, thus returning one element at a time. From MSDN documentation it states. When you use the yield keyword in a statement, you indicate […]

.NET, C#

.net, C#, csharp, dotnet

C# constructor overloading

Taswar Bhatti November 6, 2013 No Comments

In C# if one wishes to use C# constructor overloading they can use the “this” keyword right after to initialize the object, the only thing to note is one will not be able to do any validation of the data using this method. Below I have listed 3 ways that one can initialize constructor overload […]

.NET, C#

.net, C#, csharp, dotnet

LINQ tip – Ordering collection using existing array/collection using OrderBy

C# tip – Marking method or class as Obsolete/Deprecated

C# Null Coalescing Operator

C# tip property with different accessibility scopes

C# optional parameters

The using statement in C#

I refuse to answer your stupid singleton question in interview

What is the as keyword in C#? When to use it?

C# what is the yield keyword?

C# constructor overloading

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