Question

I have a public class called Profile. Very simple model class currently with 2 properties; string Name and string Fields. As I develop the project the class will expand but it’s not particularly important at the moment.

I have a Global static IList of type Profile called Profiles. I am quite new to manipulating the data in these IEnumerable types but I am looking to update one of the properties of a single profile. I have tried the following but I am receiving an object reference not set exception. The following is where I set the property:

Profiles.Single(x => x.Name == listBoxProfiles.Text).Fields = textBoxFieldName.Text;

The debugger is showing the listbox and textbox text properties both have the correct values so I think that it is the way I am using single that is wrong.

If anyone could shed some light I would be grateful.

Answer 1

A simple amendment to make the code more defensive is all that is required:

var profile = Profiles.SingleOrDefault(x => x.Name == listBoxProfiles.Text);

if (profile != null)
{
    profile.Fields = textBoxFieldName.Text;
}
else
{
    Profiles.Add(new Profile(textBoxFieldName.Text));
}

This code will cope with missing values, SingleOrDefault expects 0 or 1 items to be returned. It will throw an exception if more than 1 items are found.

If you know your code should always have the item you are looking for, then your code will work – but I’d advise against this style of programming in favour of being a little more defensive.