I am wondering if there is a special method/trick to check if a String
object is null. I know about the String.IsNullOrEmpty
method but I want to differentiate a null
String from an empty String (=""
).
Should I simply use:
if (s == null) {
// blah blah...
}
...or is there another way?
You can use the null coalescing double question marks to test for nulls in a string or other nullable value type:
textBox1.Text = s ?? "Is null";
The operator '??' asks if the value of 's' is null and if not it returns 's'; if it is null it returns the value on the right of the operator.
More info here: https://msdn.microsoft.com/en-us/library/ms173224.aspx
And also worth noting there's a null-conditional operator ?. and ?[ introduced in C# 6.0 (and VB) in VS2015
textBox1.Text = customer?.orders?[0].description ?? "n/a";
This returns "n/a" if description is null, or if the order is null, or if the customer is null, else it returns the value of description.
More info here: https://msdn.microsoft.com/en-us/library/dn986595.aspx
To sure, you should use function to check is null and empty as below:
string str = ...
if (!String.IsNullOrEmpty(str))
{
...
}
You can check with null or Number.
First, add a reference to Microsoft.VisualBasic
in your application.
Then, use the following code:
bool b = Microsoft.VisualBasic.Information.IsNumeric("null");
bool c = Microsoft.VisualBasic.Information.IsNumeric("abc");
In the above, b
and c
should both be false
.
Source: Stackoverflow.com