1. //program to display first character of string

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

namespace ConsoleApplication1
{   
    class Program
    {
        static void Main(string[] args)
        {
            string a = "abcdef";
            Console.WriteLine(a.Substring(0, 1));
            Console.ReadLine();
        }
    }
}

2. //program to demonstrate compareto method

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

namespace ConsoleApplication1
{   
    class Program
    {
        static void Main(string[] args)
        {
            string a = "abcdef";
            string b="xyz";
            Console.WriteLine(a.CompareTo(b));
            Console.ReadLine();
        }
    }
}

3. //program to demonstrate compareto method to check for equality of two strings

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

namespace ConsoleApplication1
{   
    class Program
    {
        static void Main(string[] args)
        {
            string a = "abcdef";
            string b="abcdef";
            if (a.CompareTo(b) == 0)
            {
                Console.WriteLine("Strings are equal");
            }
            else
            {
                Console.WriteLine("Strings are not equal");
            }
            Console.ReadLine();
        }
    }
}

4. //program to demonstrate Concat method of string class

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

namespace ConsoleApplication1
{   
    class Program
    {
        static void Main(string[] args)
        {
            string a = "abcdef";
            string b="abcdef";
            string c;
            c = string.Concat(a,b);
            Console.WriteLine("Concatenated String is " + c);
            Console.ReadLine();
        }
    }
}

5. //program to demonstrate Contains method of string class

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

namespace ConsoleApplication1
{   
    class Program
    {
        static void Main(string[] args)
        {
            string a = "abcdef";
            bool b;
            b = a.Contains("a");
            if (b == true)
            {
                Console.WriteLine("string a contains a");
            }
            else
            {
                Console.WriteLine("string a does not contains a");
            }
            Console.ReadLine();
        }
    }
}

6. //program to demonstrate Equals method of string class

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

namespace ConsoleApplication1
{   
    class Program
    {
        static void Main(string[] args)
        {
            string a = "abcdef";
            string b = "abcdef";
            bool c;
            c = a.Equals(b);
            if (c == true)
            {
                Console.WriteLine("both strings are equal");
            }
            else
            {
                Console.WriteLine("strings are not equal");
            }
            Console.ReadLine();
        }
    }
}

7. //program to demonstrate EndsWith method of string class

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

namespace ConsoleApplication1
{   
    class Program
    {
        static void Main(string[] args)
        {
            string a = "abcdef";
            bool b;
            b = a.EndsWith("f");
            if (b == true)
            {
                Console.WriteLine("string ends with f");
            }
            else
            {
                Console.WriteLine("string does not ends with f");
            }
            Console.ReadLine();
        }
    }
}

8. //program to demonstrate IndexOf method of string class

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

namespace ConsoleApplication1
{   
    class Program
    {
        static void Main(string[] args)
        {
            string a = "abcdef";
            int b;
            b=a.IndexOf("b");
            Console.WriteLine("Index of b in string is " + b);
            Console.ReadLine();
        }
    }
}

9. //program to demonstrate LastIndexOf method of string class

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

namespace ConsoleApplication1
{   
    class Program
    {
        static void Main(string[] args)
        {
            string a = "abcdefb";
            int b;
            b = a.LastIndexOf("b");
            Console.WriteLine("Last Index of b in string is " + b);
            Console.ReadLine();
        }
    }
}

10. //program to demonstrate Length property of string class

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

namespace ConsoleApplication1
{   
    class Program
    {
        static void Main(string[] args)
        {
            string a = "abcdefb";
            int b;
            b = a.Length;
            Console.WriteLine("Length of string is " + b);
            Console.ReadLine();
        }
    }
}

11. //program to demonstrate Replace method of string class

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

namespace ConsoleApplication1
{   
    class Program
    {
        static void Main(string[] args)
        {
            string a = "abcdefb";
            Console.WriteLine("Original String is " + a);
            a=a.Replace("a", "x");
            Console.WriteLine("Replaced string is " + a);
            Console.ReadLine();
        }
    }
}

12. //program to demonstrate StartsWith method of string class

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

namespace ConsoleApplication1
{   
    class Program
    {
        static void Main(string[] args)
        {
            string a = "abcdef";
            bool b;
            b = a.StartsWith("a");
            if (b == true)
            {
                Console.WriteLine("string starts with a");
            }
            else
            {
                Console.WriteLine("string does not starts with a ");
            }
            Console.ReadLine();
        }
    }
}

13. //program to demonstrate ToUpper method of string class

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

namespace ConsoleApplication1
{   
    class Program
    {
        static void Main(string[] args)
        {
            string a = "abcdef";
            string b;
            b = a.ToUpper();
            Console.WriteLine("upper case string is " + b);
            Console.ReadLine();
        }
    }
}

14. //program to demonstrate ToLower method of string class

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

namespace ConsoleApplication1
{   
    class Program
    {
        static void Main(string[] args)
        {
            string a = "ABCDEF";
            string b;
            b = a.ToLower();
            Console.WriteLine("lower case string is " + b);
            Console.ReadLine();
        }
    }
}

15. //program to demonstrate Trim method of string class

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

namespace ConsoleApplication1
{   
    class Program
    {
        static void Main(string[] args)
        {
            string a = "     ABCDEF      ";
            string b;
            b = a.Trim();
            Console.WriteLine("Trimmed string is " + b);
            Console.ReadLine();
        }
    }
}