Property methods vs fields in C#

Whenever a property value is accessed, the property getter will be executed. In this way, they are the same as methods that Get<PropertyName>just return a value .

If you want to avoid this, you should consider caching the value, e.g. using a lazy approach like this:

private int[] numCols = null;
public int[] NumCols
{
    get
    {
        if (numCols == null)
        {
            numCols = ExpensiveCalculation();
        }
        return numCols;
    }
}

In general, you should avoid putting expensive stuff in property getters, because the expectation for a property is that you can access the value very quickly with little overhead. If you find yourself needing a more complex process to get a value, and not suitable for caching as described above, then you should consider writing a real get method. This way the user of the method will implicitly know that there is an overhead compared to a simple property:

public int[] GetNumCols()
{
     return ExpensiveCalculation();
}