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Type of conditional expression cannot be determined because there is no implicit convertion between null and int

Posted on 2009-05-11
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Last Modified: 2013-11-07
I have a few fields that I'm reading from an excel file that could be blank (null) or with values (int or decimal).

Below is the code I've written, but it seemed like the conditional statement would not work as there is a type mismatch between the true/false statement. Is there a way to convert to a nullable type in the false statement?

Thanks in advance.  
decimal? paid = dReader["PAID_" + dynColsSuffix] == null ? null : Convert.ToDecimal(dReader["PAID_" + dynColsSuffix]);

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Question by:ngobw
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steeza earned 125 total points
ID: 24352615
The compiler is unable to determine the type of the null part of your statement.
I don't have a C# compiler handy and haven't used it in a while, but you should have 2 ways of dealing with this:

a) Cast your null to a decimal? Ie. (decimal?)null
b) Let the statement return a decimal such as 0.0 when the column is null.
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by:GuitarRich
GuitarRich earned 125 total points
ID: 24352652
Try this - or you could write your own ToDecimalNullable function that returned a decimal?

decimal? paid = dReader["PAID_" + dynColsSuffix] == null ? null : (decimal?)dReader["PAID_" + dynColsSuffix];
 

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by:tculler
ID: 24354989
I think what the problem here is that index of dReader is returning a struct of some kind. A struct cannot be compared to null. What is the exact type of "dReader"?

The last part of your statement (the Convert.ToDecimal) is not your problem here--there is always an implicit conversion from a non-nullable into a nullable (just not vice versa -- use the Coalesce operator ( "??")).
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