LINQ to Entities does not recognize the method 'System.TimeSpan Subtract(System.DateTime)

Question

The following throws an error:

public FieldViewer GetFieldViewByFieldIDIPAndUserByDate( int fieldID, string ip, string userID, DateTime date )
{
    return this.         


        

Answer 1

EntityFunctions.DiffMinutes for your case will be inefficient. You should do this way

public FieldViewer GetFieldViewByFieldIDIPAndUserByDate( int fieldID, string ip, string userID, DateTime date )
{
    var tenMinThreshold = date - TimeSpan.FromMinutes(10);
    return this.context.FieldViewers.Where( x =>
        x.Field.FieldID == fieldID &&
        x.Viewer.IPAddress == ip &&
        x.Viewer.User.Id == userID &&
        x.Viewer.CreatedAt <= tenMinThreshold).FirstOrDefault();
}