Entity Frame Core ExecuteUpdate Compiling error

Question

The following codes are all working great!

string? newval = null;
indexDB.TabeABC
    .Where(b => b.PropertyABC != null)
    .ExecuteUpdate(setters => setters.SetProperty(b => b.PropertyABC, newval));

However, this does not even pass compiler.

indexDB.TabeABC
    .Where(b => b.PropertyABC != null)
    .ExecuteUpdate(setters => setters.SetProperty(b => b.PropertyABC, null));

I do not understand why though, could someone give me a little explanation.

Thanks a million!

Answer 1

Hi,@Ning Zhu. Welcome to Microsoft Q&A. 

As the compilation error message describes, your second way of writing will be ambiguous.

 

SetProperty has overloaded methods.

.SetProperty<TProperty>(Func<TSource, TProperty>, Func<TSource, TProperty>)

 

.SetProperty<TProperty>(Func<TSource, TProperty>, TProperty)

null could be assigned to both Func<TSource, TProperty> and TProperty. The compiler cannot identify which function to execute, so it reports an error of CS0121.

 

As described in the CS0121 document, forced conversion could solve this problem.

indexDB.TabeABC

    .Where(b => b.PropertyABC != null)

    .ExecuteUpdate(setters => setters.SetProperty(b => b.PropertyABC, (string)null));

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