EF Non-static method requires a target

Question

I\'ve serious problems with the following query.

context.CharacteristicMeasures
        .FirstOrDefault(cm => cm.Charge == null &&
                        


        

Answer 1

Try moving newAreaItem == null outside of the query

bool newAreaItemIsNull = (newAreaItem == null);

and replace newAreaItem == null with newAreaItemIsNull in query.

Query parser can only operate with the objects in the database, and newAreaItem is not one of them.

Answer 2

I had the exact same problem as you have when newAreaItem == null is true.

The problem comes from the fact that the item used in the LINQ cannot be null. Thus, when newAreaItem == null is true it means that newAreaItem is null and this leads to the error being thrown.

All you can do in my opinion is, after checking newAreaItem == null, to set the newAreaItem to a new empty object of that type if newAreaIteam is null. The newAreaItemIsNull condition will still be in place, thus the

(cm.AreaItem != null && cm.AreaItem.Id == newAreaItem.Id)

in your code below will still not be evaluated if newAreaItem is null.

context.CharacteristicMeasures.
                                 FirstOrDefault(cm => cm.Charge == null &&
                                                      cm.Characteristic != null && cm.Characteristic.Id == c.Id &&
                                                      cm.Line != null && cm.Line.Id == newLine.Id &&
                                                      cm.ShiftIndex != null && cm.ShiftIndex.Id == actShiftIndex.Id &&
                                                      (newAreaItem == null ||
                                                       (cm.AreaItem != null && cm.AreaItem.Id == newAreaItem.Id)));