C# Lambda Problem

Question

Probably something simple, but as I'm new to lambda expressions, the problem evades me:

m => m.contactID == contactID && m.primaryAddress == true && (m.addressTypeID == 2 || m.addressTypeID == 3)

I tried to use that lambda expression but I receive an invalid operator. Is there a way to simplify this so that it would work?

Edit:

The equivolent sql query would be:

SELECT *
FROM Contact
WHERE contactID = 3
AND primaryAddress = 1
AND (addressTypeID = 2 OR addressTypeID = 3)

I have a repository function defined like so:

public E Single(Expression<Func<E, bool>> where)
{
 return objectSet.Single<E>(where);
}

I'm passing the lambda expression above into this function:

myRepository.Single(m => m.contactID == contactID && m.primaryAddress == true && (m.addressTypeID == 2 || m.addressTypeID == 3));

• user60456: What are you trying to do? Can you post some more information/code?
• Reed Copsey: Also, please post the full text of the error you're receiving.
• nothrow: is m.primaryAddress != null (or !string.IsNullOrEmpty(m.primaryAddress)) what you meant? EDIT: if primaryAddress is integer, you cannot compare it to true/false.
• Reed Copsey: Is this a compiler error, or a runtime error? If runtime, it's most likely that there is more than a single element...
• Chris Klepeis: Runtime - I'll double check but I'm pretty darn positive its returning only 1 item.

Answer 1

If you are receiving an InvalidOperationException, the most likely cause is that there is more than one record that matches your criteria.

Queryable.Single will raise InvalidOperationException if there is more than a single correct value. In this case, try using .First(m => ..) instead:

myRepository.First(m => 
 m.contactID == contactID && 
 m.primaryAddress == true && 
 (m.addressTypeID == 2 || m.addressTypeID == 3)
 );

This will return the first matching result, if there are more than one. If you need to handle no matches, look into FirstOrDefault (which will return null if there are no matches).

Answer 2

m.primaryAddress == true looks suspicious. is m.primaryAddress really a bool property?

• Chris Klepeis: its a bit operator in the database
• Meiscooldude: It could be, perhaps would be better named IsPrimaryAddress. But really, You should just write "&& m.primaryAddress &&" instead of "&& m.primaryAddress == true &&", since it is a bool.
• Meiscooldude: a bit operator? is it nullable?

Answer 3

m => (m.contactID == contactID && m.primaryAddress == true && (m.addressTypeID == 2 || m.addressTypeID == 3)) is merely a boolean expression.

You need to do something like list.Remove(m => (m.contactID == contactID && m.primaryAddress == true && (m.addressTypeID == 2 || m.addressTypeID == 3))) etc

This says take each item in my list as m if this returns true remove m

Edit OP reposted while I was writing that answer

I would write this like this as to your syntax.

Func Filter<var, bool> = m => (m.contactID == contactID && m.primaryAddress == true && (m.addressTypeID == 2 || m.addressTypeID == 3))

then pass Filter into your myrepository.Single(Filter)

Answer 4

From your SQL query, should it be:

m => m.contactID == contactID && m.primaryAddress == 1 && (m.addressTypeID == 2 || m.addressTypeID == 3)