How to assign empty string if the value is null in linq query?

Question

I have following LINQ query to get a set of data.

var fields = from row in datarows
from field in row
from col in columnnames
where field.Key == col
select new { ColumnName = col, FieldValue = field.Value };

The problem is that my code that handle the fields after this query fails because field.Value of some rows are returning null.

My goal is to assign an empty string if null is detected.

Something like if field.Value == null, then field.Value = ""

Is it possible to do so in linq query?

Jon · Accepted Answer · 2013-05-10 20:42:58Z

37

Use the null coalescing operator ??:

FieldValue = field.Value ?? ""

answered May 10, 2013 at 20:42

Jon

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10 Comments

PSL Over a year ago

hey @Jon any specific reason using "" over string.Empty?

Jon Over a year ago

@PSL: 10 chars less to type.

cgalvao1993 Over a year ago

Is there a way where I can do this with integers?

Jon Over a year ago

@CássioGalvão: Can you be more specific? Value types cannot be null so what exactly do you have in mind?

cgalvao1993 Over a year ago

@Jon, It works with strings, but if 'field.Value' is an integer, I get the message: "Operand '??' cannot be applied to operands of type 'int' and 'int'. How do I set default values of integer types? I'm using linq

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Justin Niessner · Accepted Answer · 2013-05-10 20:42:53Z

6

FieldValue = field.Value ?? String.Empty

answered May 10, 2013 at 20:42

Justin Niessner

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Comments

Claudio Redi · Accepted Answer · 2013-05-10 20:43:09Z

4

Use the null-coalescing operator

select new { ColumnName = col, FieldValue = field.Value ?? string.Empty };

The ?? operator is called the null-coalescing operator and is used to define a default value for nullable value types or reference types. It returns the left-hand operand if the operand is not null; otherwise it returns the right operand.

answered May 10, 2013 at 20:43

Claudio Redi

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Comments

Daniel Möller · Accepted Answer · 2013-05-10 20:43:14Z

4

FieldValue = field.Value == null ? "" : field.Value

answered May 10, 2013 at 20:43

Daniel Möller

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1 Comment

Daniel Möller Over a year ago

...all answers better than mine. Learned something.

PSL · Accepted Answer · 2013-05-10 20:43:10Z

1

Use ?? operator to return Empty string in case of null

var fields = from row in datarows
from field in row
from col in columnnames
where field.Key == col
select new { ColumnName = col, FieldValue = (field.Value ?? string.Empty) };

answered May 10, 2013 at 20:43

PSL

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Comments

arunlalam · Accepted Answer · 2013-05-10 20:44:59Z

0

var fields = from row in datarows
from field in row
from col in columnnames
where field.Key == col
select new { ColumnName = col, FieldValue = field.Value == null ? string.Empty: field.Value};

answered May 10, 2013 at 20:44

arunlalam

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Comments

mfsumption · Accepted Answer · 2019-07-24 05:09:36Z

0

I also learned that if you are concatenating two fields in a linq field assignment and you are using the null-coalescing operator on only one of the fields, then you need to put parentheses around the field statement as such:

StreetAddr = customer.StreetAddr + ", " + (customer.Suite ?? "")

However, this code is not so great either because if the "Suite" field is null, then I still got that comma-space ", " hanging out after the "StreetAddr" field. Wish I knew a way to fix that?

answered Jul 24, 2019 at 5:09

mfsumption

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2 Comments

mfsumption Over a year ago

So this is one way to fix that: StreetAddr = customer.StreetAddr + (string.IsNullOrEmpty(customer.Suite) ? "" : ", " + customer.Suite)

mfsumption Over a year ago

Now some may argue that it's bad to concatenate fields in linq field assignments, and that I should use properties in the view model to concatenate fields instead. I agree, but sometimes I'm lazy and do it anyway. :-)

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