I get CA1820 "Test for empty string using string length"

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.NET4.5

When I run code analysis I get CA1820 and wanted to see if there are better options for writing the following block of code.

C#

if (dataFileLine.Length == NUM_COLUMNS)
{
     if (dataFileLine[10].Trim() == string.Empty
     || dataFileLine[15].Trim() == string.Empty
     || dataFileLine[21].Trim() == string.Empty
     || dataFileLine[32].Trim() == string.Empty)
     continue;
}

Gary

Posted 9-Jun-14 9:34am

Prgx

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DamithSL 9-Jun-14 23:00pm

what if all file lines having spaces( not empty), is it valid?

2 solutions

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Kornfeld Eliyahu Peter · Accepted Answer · 2014-06-09T09:52:00

This is a performance suggestion by code analysis...
The idea is to use IsNullorEmpty() method instead of == Empty.
In your case:

C#

if (string.IsNullOrEmpty(dataFileLine[10])
  || string.IsNullOrEmpty(dataFileLine[15])
  || string.IsNullOrEmpty(dataFileLine[21])
  || string.IsNullOrEmpty(dataFileLine[32])

For reference - http://msdn.microsoft.com/en-us/library/ms182279.aspx[^]

Dave Kreskowiak · Accepted Answer · 2014-06-09T09:49:00

Solution 1

It's telling you to check for an empty string by checking its Length, not comparing it to the reference of String.Empty.

if (dataFileLine[10].Trim().Length == 0
    || dataFileList[15].Trim().Length == 0
....

The tiny little problem with that is if any of those dataFileLine[] references returns null the call to Trim will fail with a "Object not set to an instance of an object" error.

Posted 9-Jun-14 9:49am

Dave Kreskowiak

Updated 9-Jun-14 9:51am

v2

Comments

Kornfeld Eliyahu Peter 9-Jun-14 16:08pm

I didn't got you. If string is null any non static property/method - including Length - will fail with null reference exception. The code you propose here will fail on Trim() if dataFileLine[n] is null...
We deal here with a code analysis message that badly phrased...

Prgx 9-Jun-14 18:55pm

Thank you for explaining this, I will use your suggestion and provide feedback.
I also agree,the code analysis phrase needs improvement.

Gary