CODEWITHSUNDEEP
c#lambda
sambomartin
sambomartin

Reputation: 6813

Property Lambda expression gets an additional Convert(p=>p.Property)

I have a problem where in some cases (appears to be where property type is bool) a lambda expression used to refer to a property. I use this to get its name; the problem is sometime the expression is getting modified to have an additional Convert() function.

e.g.

GetPropertyName<TSource>(Expression<Func<TSource, object>> propertyLambda) {...}

var str = GetPropertyName<MyObject>(o=>o.MyBooleanProperty);

What's happening it that the propertyLambda looks like Convert(o.MyBooleanProperty) and not o.MyBooleanProperty that i'd expect.

Upvotes: 4

Views: 344

Answers (1)

svick
svick

Reputation: 244767

The Convert is added, because o.MyBooleanProperty is a bool, but the result has to be an object. If you made your method generic both in the source object type and the result type, then there would be no Convert:

GetPropertyName<TSource, TResult>(Expression<Func<TSource, TResult>> propertyLambda)

Unfortunately this means you have to specify TResult explicitly:

GetPropertyName<MyObject, bool>(o => o.MyBooleanProperty)

If you don't want to do that, you would have to find some way to infer MyObject, or avoid needing it.

For example, if the current object is MyObject (and you're in an instance method), you could change your code to take Func<TResult>:

GetPropertyName(() => this.MyBooleanProperty)

Or you could include another parameter of type TSource that will help you infer the type:

GetPropertyName(myObject, o => o.MyBooleanProperty)

Upvotes: 3

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