Difference between ref and out parameters

Understand the differences between ref and out parameters in C#, with guidance on when to use each.

The ref Keyword

The ref keyword passes a variable by reference, requiring it to be initialized before being passed, and allows the method to read and modify its value.

The out Keyword

The out keyword also passes a variable by reference, but does not require it to be initialized beforehand, since the called method is expected to assign it a value.

Key Differences

The main difference is that ref requires the variable to already have a value going in, while out does not, and out is typically used when a method needs to return multiple values.

When to Use Each

Use ref when a method needs to both read and update an existing value, and use out when a method's main purpose is to produce one or more new values for the caller.