Create own function that checks for null value and returns an empty string

Question

If I have a class like below, how would I create the function nullToEmptyString()?
If object is DBNull.Value then return an empty string, otherwise return the value. The function should work on every object in person.

public class Person
{
    public object surname { get; set; }
    public object lastname { get; set; }
    public object zip_code { get; set; }
    public object tele { get; set; }
}

I retrieve a list of persons from the DB and I want to print the value, if it has a value, otherwise an empty string.

foreach (var person in listFromDB)
{
    person.surname.nullToEmptyString()
    person.lastname.nullToEmptyString()
}

EDIT
In short, this function should work like the .ToString() function but would also be able to handle DBNull values.

A string is immutable, so you cannot change the current instance. You'll have to use a syntax like: person.surname = person.surname.nullToEmptyString(); — Arjen
– Arjen, Commented Jun 9, 2011 at 9:02
Nopes. They both are valid. it depends whether you wish to modify the person class values or you want to display. If you wish to modify, you need to do as suggested by @Arjen, or else I have just displayed the values which can even be taken in separate variables. — Ashish
– Ashish, Commented Jun 9, 2011 at 9:20

Ashish · Accepted Answer · 2011-06-09 09:21:56Z

1

public static string nullToEmptyString(this string dbStr)
{
    return (dbStr == null || dbStr == "") ? "" : dbStr;
}

foreach (var person in listFromDB)
{
    Response.Write(person.surname.nullToEmptyString());
    Response.Write(person.lastname.nullToEmptyString());
}

Hope this helps.

edited Jun 9, 2011 at 9:21

answered Jun 9, 2011 at 8:57

Ashish

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5 Comments

Niklas Over a year ago

ah, so this points to the object you run .nullToEmptyString() on?

Ashish Over a year ago

Yes. This is a new fundamental kin C# 3.0 called as extension methods.

Niklas Over a year ago

Where should I create this function? I get the error Extension method must be defined in a non-generic static class if I try to make it a function in my Person class.

Ashish Over a year ago

Ah yes. Forgot. You can create a new static class and define the above method as static.

Niklas Over a year ago

Yep, works like a charm =). I only need it for print and not to actually change the type.

Lasse Edsvik · Accepted Answer · 2011-06-09 08:58:55Z

1

Try something like

public string Somename(this string somestring)
{
      return somestring ?? "";
}

answered Jun 9, 2011 at 8:58

Lasse Edsvik

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