How to avoid Tostring exception if string is null?

Question

I want to convert the data row value to sring as follows.

userGuid = dr["user_guid"].ToString();

It may contains Guid or null(Not string empty). If it contains null i got the exception.

How can i overcome this..

@AndroidNoobie I try that it works for empty string.But for null it does not working — Venkatesh, Jan 25 '19 at 05:24
There are lot of examples, for example `dr["user_guid"]?.ToString();`. — SᴇM, Jan 25 '19 at 05:26
See the example from SeM.https://blogs.msdn.microsoft.com/jerrynixon/2014/02/26/at-last-c-is-getting-sometimes-called-the-safe-navigation-operator/ — Andrew, Jan 25 '19 at 05:29

Manoj Choudhari · Accepted Answer · 2019-01-25T10:07:18.797

2

I guess you are reading from data reader.

You will have to check if the value is null or DBNull and then you can call to string method.

    string user_guid = dr["user_guid"] != DBNull.Value && dr["user_guid"] != null ? dr["user_guid"].ToString() : null ;

Hope this helps.

edited Jan 25 '19 at 10:07

answered Jan 25 '19 at 05:33

Manoj Choudhari

CCD · Answer 2 · 2019-01-25T05:33:25.633

1

if (dr[user_guid"] != null) {
    //whatever you want to do
} else {
    //handle the null value in some way
}

Alternatively,

dr["user_guid"]?.ToString();

The ? is what's called a "null-safe navigator".

edited Jan 25 '19 at 05:33

answered Jan 25 '19 at 05:25

CCD

I try this also i want to use this conversion in many places. So this lead too much of code.I want simple solutions – Venkatesh Jan 25 '19 at 05:28
2

This is a simple solution. If a standard check for a null value is too much, I'm not sure what exactly you could possibly be expecting. – CCD Jan 25 '19 at 05:30
I know this is simple question.I just want to done this by single line of code or by overriding in only one place – Venkatesh Jan 25 '19 at 05:34

Anu Viswan · Answer 3 · 2019-01-25T05:40:41.733

0

This might be useful, one of many ways

 userGuid  = dr["user_guid"]?.ToString()?? "Default Value";

Please do replace "Default Value" with whatever you feel is appropriate according to your application logic.

edited Jan 25 '19 at 05:40

answered Jan 25 '19 at 05:34

Anu Viswan

score -1 · Answer 4 · answered Jan 25 '19 at 05:26

-1

Maybe this: userGuid = dr["user_guid"].ToString() ?? throw new Exception();

answered Jan 25 '19 at 05:26

He wants to avoid exceptions. – Andrew Jan 25 '19 at 05:29
Sorry. No problem. `userGuid = dr["user_guid"].ToString() ?? "";` – Johannes Krauser III Jan 25 '19 at 05:32
No worries mate. – Andrew Jan 25 '19 at 05:33

4 Answers4