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In previous posts we discussed about the building blocks of C# and how we can get started using Visual Studio to build and debug your applications. In this post we are going to continue our learning journey further.

"One learns from books and example only that certain things can be done. Actual learning requires that you do those things" – Frank Herbert

Day 3 to Day 5

String Formatting

Getting a basic knowledge on various string formatting options available in C# is important. No matter the number of years of experience we gain, we will still be writing code which uses various string formats. We will be using string format options while writing log files, displaying messages in console window, displaying text and currency formats in our websites and more. Our relationship with string formatting in C# will continue as long as we code.

So how do we format strings in C#?

string first = "a";
string second = "test";
string last = "message";
Console.WriteLine(string.Format("This is {0} {1} {2}", first, second, last));

The above code will display the message as "This is a test message".

Strings in C# are immutable. We will keep getting this question in every interview one way or other.

Let us see this with an example.

string firstMessage = "message1";
string secondMessage= "message2";
//Compiler will create another location to store the result for secondMessage
secondMessage =  firstMessage + secondMessage;

In these scenarios, it is recommended to use StringBuilder. StringBuilder is part of System.Text Namespace. The same example can be created using the Append method of StringBuilder.

StringBuilder test = new StringBuilder();
test.Append("message1");
test.Append("message2");

We can also use AppendLine if we want to add text to the newline.

Date Time Operations

DateTime Operations can be performed in C# using System.DateTime. We can also apply various string formats while performing date time operations. We can initialize DateTime with and without options to create date objects as per our requirement.

Check out the resources section for additional information on Date Time Operations.

Statements in C#

C# supports the following Control Flow Statements and Iteration Statements. It is important to get an understanding of these, because we will be using them as long as we are programming using C#.

Control Flow Statements

If-Else
Switch - Case

Iteration Statements

For Loop
ForEach Loop
While Loop
Do-While Loop

Getting an idea of Control Flow and Iteration Statements will help us, because we will be using these statements while writing code to implement various scenarios. Check out the resource section for more information on Statements.

Arrays and Collections

Arrays can be used to store group of items which belong to the same type. We can create integer arrays, string arrays and many. Arrays in C# support a maximum of 32 dimensions.

int[] numberArray = new int[5]{1,2,3,4,5};

In the above snippet we are creating a single dimension array called numberArray which can store only integer values. The array is defined with maximum length of 5. This is called fixed length array. The array has 5 items 1,2,3,4,5.

We can access items from an array by mentioning the index. The below code snippet retrieves the item which is present in first position ,third position and fifth position.

Console.WriteLine(numberArray[0]);
Console.WriteLine(numberArray[2]);
Console.WriteLine(numberArray[4]);

In C# the index starts from zero. If we try to access an item by using an index beyond the length of array will result in IndexOutofRangeException.

Console.WriteLine(numberArray[6]);

ArrayList can be used to store items of different type. ArrayList is currently not recommended to use. We can use List in place of ArrayList. List is present as part of System.Collections.Generic namespace. With List we can store objects which are type safe.

List<string> stringList = new List<string>();
stringList.Add("message1");
stringList.Add("message2");

Console.WriteLine(stringList.Count);
Console.WriteLine(stringList[1]);

In above code snippet, we are creating a List collection which is of type string. After initializing the collection we are adding two items. We can access the number of items in the collection using the Count. We get the item at second position by mentioning the index.

using System;
using System.Collections.Generic;
using System.Linq;

namespace myApp
{
    class Program
    {
        static void Main()
        {
          Employee firstobject = new Employee(){Name="test",Id=1};
          Employee secondobject = new Employee(){Name="test2", Id=2};
          List<Employee> empList = new List<Employee>();
          empList.Add(firstobject);
          empList.Add(secondobject);
          Console.WriteLine(empList.Count);        
        }
    }

    public class Employee
    {
        public string Name;
        public int Id;
    }
}

With List we can create Collections of any type. The above snippet we are creating two objects of Emp class by providing their values. We are creating an empty list called empList. Then we are adding the objects to empList. The program will print the count of items from empList.

Check the resources section for additional information on List and various operations that can be performed with List.