Ref Parameter: Used to pass a parameter as a reference so that the function called will set the value. This could be used to return more than 1 value by a function.
e.g.
public int AddMuliply( int a , int b, ref int c)
{
c = a*b;
return ( a+b);
}
The above function, returns the addition of two numbers as well as computes the multiplication result and passes to the calling function.
Out Parameter: Used to pass values from the aspx Code-behind to the aspx page.
The difference is that for a ref parameter, you have to assign a value before you call the function, while for OUT parameter, you dont have to assign a value, the calling function assumes that the called function would assign some value.
A ref parameter must first be initialized before being passed from the calling function to the called function. but a out parameter need not be initialized, we can pass it directly when we pass a parameter as ref to a method, the method refers to the same variable and changes made will affect the actual variable.
even the variable passed as out parameter is same as ref parameter, but implementation in c# is different, Arguement passed as ref parameter must be initialized before it is passed to the method. But in case of out parameter it is not necessary. But after a call to a method as out parameter it is necessary to initialize.
When to use out and ref parameter, out parameter is used when we want to return more than one value from a method. Ref parameter can be used as both input and o/p parameter out parameter can be used as only output parameter
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