Shortest way to check for null and assign another value if not
C#.NetNullVariable AssignmentC# Problem Overview
I am pulling varchar
values out of a DB and want to set the string
I am assigning them to as "" if they are null
. I'm currently doing it like this:
if (string.IsNullOrEmpty(planRec.approved_by) == true)
this.approved_by = "";
else
this.approved_by = planRec.approved_by.toString();
There seems like there should be a way to do this in a single line something like:
this.approved_by = "" || planRec.approved_by.toString();
However I can't find an optimal way to do this. Is there a better way or is what I have the best way to do it?
C# Solutions
Solution 1 - C#
Try this:
this.approved_by = IsNullOrEmpty(planRec.approved_by) ? "" : planRec.approved_by.toString();
You can also use the null-coalescing operator as other have said - since no one has given an example that works with your code here is one:
this.approved_by = planRec.approved_by ?? planRec.approved_by.toString();
But this example only works since a possible value for this.approved_by
is the same as one of the potential values that you wish to set it to. For all other cases you will need to use the conditional operator as I showed in my first example.
Solution 2 - C#
You are looking for the C# coalesce operator: ??. This operator takes a left and right argument. If the left hand side of the operator is null or a nullable with no value it will return the right argument. Otherwise it will return the left.
var x = somePossiblyNullValue ?? valueIfNull;
Solution 3 - C#
Starting with C# 8.0, you can use the ??= operator to replace the code of the form
if (variable is null)
{
variable = expression;
}
with the following code:
variable ??= expression;
More information is here
Solution 4 - C#
The coalesce operator (??) is what you want, I believe.
Solution 5 - C#
My guess is the best you can come up with is
this.approved_by = IsNullOrEmpty(planRec.approved_by) ? string.Empty
: planRec.approved_by.ToString();
Of course since you're hinting at the fact that approved_by
is an object
(which cannot equal ""), this would be rewritten as
this.approved_by = (planRec.approved_by ?? string.Empty).ToString();
Solution 6 - C#
With C#6 there is a slightly shorter way for the case where planRec.approved_by is not a string:
this.approved_by = planRec.approved_by?.ToString() ?? "";
Solution 7 - C#
Use the C# coalesce operator: ??
// if Value is not null, newValue = Value else if Value is null newValue is YournullValue
var newValue = Value ?? YourNullReplacement;
Solution 8 - C#
To extend @Dave's answer...if planRec.approved_by is already a string
this.approved_by = planRec.approved_by ?? "";
Solution 9 - C#
To assign a non-empty variable without repeating the actual variable name (and without assigning anything if variable is null!), you can use a little helper method with a Action
parameter:
public static void CallIfNonEmpty(string value, Action<string> action)
{
if (!string.IsNullOrEmpty(value))
action(value);
}
And then just use it:
CallIfNonEmpty(this.approved_by, (s) => planRec.approved_by = s);
Solution 10 - C#
The accepted answer was correct in time, when it was given.
For people still finding this question: Today you can use the ??= Operator.
e.g:
private string _test = null;
private void InitIfNull(){
_test ??= "Init";
}
Solution 11 - C#
You can also do it in your query, for instance in sql server, google ISNULL
and CASE
built-in functions.
Solution 12 - C#
I use extention method SelfChk
static class MyExt {
//Self Check
public static void SC(this string you,ref string me)
{
me = me ?? you;
}
}
Then use like
string a = null;
"A".SC(ref a);