As per Object Oriented Programming principles internal of class should be hidden from outside world. So it is recommended to wrap fields of a class with properties, get,set in C# and keep fields private. By doing this object fields are safe and we can do some processing, event invocation, validation etc. while changing value of a field using properties or get set functions.

Here is sample for wrapping field into c# properties

    public class SampleClass
    {
        // this is a field.  It is private to your class and stores the actual data.
        private string _myField1;

        // this is a property.  When you access it uses the underlying field, but only exposes
        // the contract that will not be affected by the underlying field
        public string MyField1
        {
            get
            {
                return _myField1;
            }
            set
            {
                _myField1 = value;
                OnChangeField1();
            }
        }

        private void OnChangeField1()
        { 
            //Some code
        }
    }

In above code we can do processing and other code execution in get and set block.

In C# 3.0 AutoProperty is introduced in which we do not need to declare field separately, we have to just write property with modified syntax. C# 3.0 and above compiler will generate a private field automatically into compiled assembly.

Ref: http://msdn.microsoft.com/en-IN/library/bb384054.aspx

    public class SampleClass
    {
        public string MyField1
        {
            get;
            set;
        }
    }

Above two examples will produce same IL code.