Question

I have a class with like 20 fields which get populated from SQL database on load. Currently I am calling load data method right after the constructor, which calls SQL proc and populate all the required fields. At times, I may not access the these 20 fields at all, I am adding additional cost of SQL call even though it was not required. So I changed all the properties to have an associated private property and when the program calls the public property, first I check the private property and if it is null that means we need to load data from sql so I call the load method. It works great, but when I see the code, there is a repeated pattern of null check and load the sql query. Is there a better way of doing this?

private string _name;
public string Name 
{
   get {
      if (_name == null)
         LoadData(); //this popultes not just but all the properties
      return _name;
   }
}

Answer 1

Nope, this is right. Here is the wikipedia article. The overhead of the null check will be very minimal compared to unnecessary database calls. Now, if the users of the program actually use the values 99% of the time, then I would say this pattern is not needed.

Just one note of caution: If any of your values could possibly be null, then you will make unnecessary database calls. It might be better to do something like this (which will be an even quicker check since it is just a bit check):

//Constructor default to not loaded
bool isLoaded = false;

private string _name;
public string Name 
{
   get {
      if (!isLoaded)
         LoadData(); //this popultes not just but all the properties
      return _name;
   }
}   

private LoadData()
{
    //Load Data
    isLoaded = true;
}