Question

I have the following code which gives the warning in the title. I am pretty sure I have done something like this before but it didnt give any warning. I would like to ask two things of those posting. 1) What here would cause a problem? 2) Does it need to be fixed?

The reason I ask is that this code works fine as I expect it to so clearly this warning is not causing an issue. I cannot stand to have warnings etc in my code though and so would like a solution to this but I also want to know why this warning occurs and if it is harmful in any way.

Code:

 public class AttributeType
 {
      private string m_attributeNameField;

      public string AttributeName
      {
          get { return m_attributeNameField; }
          set { m_attributeNameField = value; }
      }
 }

 private StandardResponseType ValidateAttributes(string featureType, IEnumerable<AttributeType> attributeList, string userCategory)
 {
       StandardResponseType standardResponse = 
       new StandardResponseType(DateTime.Now.ToString(CultureInfo.InvariantCulture), "RWOL_UTILS.Get_Item_Attributes", "", "OK");

        if (attributeList.Any())
        {
            foreach (AttributeType attribute in attributeList)
            {
                if (attribute.AttributeName == null) continue;
                {
                    //do stuff
                }
            }
        }
        else
        {
            standardResponse.Message = "Error: No attributes passed in the list. ValidateAttributes().";
            standardResponse.ResponseCode = "FAIL";

            return standardResponse;
        }
}

EDIT: There is more code in the method but it doesn’t have a bearing on this issue.

UPDATE: I had to add the follwing code to make this work. Why is it more efficient to add this? If I have to count and read the new list then what is the difference between doing that and doing it on the original item? The list is only ever passed once. I could understand this issue if the list was populated within the method but is isnt. It is just passed in already filled.

List<AttributeType> newlist = attributeList.ToList();

if (newlist.Count() != 0)
{
    foreach (AttributeType attribute in newlist)
............

Answer 1

The possible problem depends on where your IEnumerable comes from. Some data sources might only allow for a single enumeration or they might be expensive (maybe some database query), which would be already started by attributeList.Any().

You can just remove the Any() check, because if there are no elements in your IEnumerable , your loop won’t run anyway (assuming your example shows the complete picture and there is no other logic dependent on the check).

EDIT: Based on your edited question, you cannot remove the check. But, you can use attributeList.ToArray() to convert your IEnumerable to an array which you then work with and get rid of the warning.