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[Source] Cast to value type "System.Decimal" failed...

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Posted on 3/11/2019 10:02:24 AM | | | |
The cast to the value type "System.Decimal" fails because the materialized value is null. The generic parameter or query of the result type must be of a type that can be null.
1. When using EF to access database summing, such exceptions are often encountered

An unhandled exception of type "System.InvalidOperationException" occurs in EntityFramework.dll



Exception Code 1:



Exception code 2:

2. Reasons:

Reason for throwing: The data filtered from the database according to the conditions is empty, and then the sum throws an exception.

Solution 1:After the filter fields or data rows are taken into memory based on the criteria, they are summed


Solution 2:This can be done if the sum results need to be specified as null when the filter data rows do not exist based on the condition



Solution 3 (recommended):Use DefaultIfEmpty()








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Posted on 3/11/2019 11:38:22 AM |
I'm using option three
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