Difference between Property and Field in C# 3.0+

Fields and properties look the same, but they are not. Properties are methods and as such there are certain things that are not supported for properties, and some things that may happen with properties but never in the case of fields.

Here's a list of differences:

• Fields can be used as input to out/ref arguments. Properties can not.
• A field will always yield the same result when called multiple times (if we leave out issues with multiple threads). A property such as DateTime.Now is not always equal to itself.
• Properties may throw exceptions - fields will never do that.
• Properties may have side effects or take a really long time to execute. Fields have no side effects and will always be as fast as can be expected for the given type.
• Properties support different accessibility for getters/setters - fields do not (but fields can be made readonly)
• When using reflection the properties and fields are treated as different MemberTypes so they are located differently (GetFields vs GetProperties for example)
• The JIT Compiler may treat property access very differently compared to field access. It may however compile down to identical native code but the scope for difference is there.

Encapsulation.

In the second instance you've just defined a variable, in the first, there is a getter / setter around the variable. So if you decide you want to validate the variable at a later date - it will be a lot easier.

Plus they show up differently in Intellisense :)

Edit: Update for OPs updated question - if you want to ignore the other suggestions here, the other reason is that it's simply not good OO design. And if you don't have a very good reason for doing it, always choose a property over a public variable / field.

A couple quick, obvious differences

1. A property can have accessor keywords.

   public string MyString { get; private set; }
   

2. A property can be overridden in descendents.

   public virtual string MyString { get; protected set; }