Why we need to Filter the contents recursively

Question

I have an application in which some sides i am using Filter conditions,,But i dont know the meaningof usage of word "recursive" in that filter conditions Here is a bit of code

          // Indicates a recursive filter.  Only valid for object type property filters.
      private bool m_recursive = false;
------------------------
      /// <summary>
      /// Method to apply an object filter to an object.
      /// </summary>
      /// <param name="myObject">the object to which to apply the filter</param>
      /// <returns>true if the object passes the filter, false otherwise</returns>
      public bool Apply(DataModelObject myObject) 
      {


----------------------




      /// Method to apply a property filter
      /// </summary>
      /// <param name="myObject">the object to which to apply the filter</param>
      /// <param name="filteredType">type of the object to which to apply the filter</param>
      /// <returns>true if the object passes the property filter, false otherwise</returns>
      public bool Apply(DataModelObject myObject, Type filteredType)
      {




switch( FilterType )
                  {
                     case enumFilterType.regularExpr:
                     switch( Operator )
                     {
                        case enumOperator.eq:

------------------------------------
case enumFilterType.strExpr:
                     switch( Operator )
                     {
                        case enumOperator.eq:
-------------------------------------
case enumFilterType.objectFilt:
do
                           {
                              retval = ((ObjectFilter)m_filterValue).Apply(propVal);
                              myObject = propVal;
                              if (m_recursive && retval == false && myObject != null)
                              {
                                 propVal = (DataModelObject)prop.GetValue(myObject, null);
                              }
                              else
                              {
                                 myObject = null;
                              }
                           } while (myObject != null);
                        }
                        if( m_operator == enumOperator.ne )
                        {
                           retval = !retval;
                        }
-----------------------
      public object Clone()
      {
         clone.m_recursive = this.m_recursive;
         return clone;
      }

Can any one tell me why recursive false is using here

Answer 1

The important part of you code is this:

do
{
  retval = ((ObjectFilter)m_filterValue).Apply(propVal);
  myObject = propVal;
  if (m_recursive && retval == false && myObject != null)
  {
     propVal = (DataModelObject)prop.GetValue(myObject, null);
  }
  else
  {
     myObject = null;
  }
} while (myObject != null);

Basically, when the FilterType is objectFilt then the code goes into a do...while loop which is a loop of code that is always run at least once, because the recursing condition (in this case, myObject != null) is checked after the loop code has been executed once.

If m_recursive is false then retval and myObject are ignored and myObject is set to null, so when the recursing condition is checked, it fails and the loop exits.

If m_recursive is set to true, the setting myObject to null is determined by two things: myObject being null and retval being false.

retval is set by m_filterValue.Apply(propVal). It's not clear where propVal comes from.

In case you're unaware of what recursion is, it is where a piece of code causes its self to be run again. In your code, this is represented by the do...while loop.