assign custom list by value memory allocation in c# list object assignment issue

Question

objTempList = objParentList;
foreach (var item in objTempList)
{
    objChildList = objList.AsQueryable()
                          .Where(x => x._parentId == item.filedbid)
                          .ToList<FileObjectView>();
    if (objChildList != null)
    {
        foreach (var child in objChildList)
        {
            objParentList.Add(child);
        }
    }
}

Above is my code, problem is the assignment of objTempList = objParentList

objParentList has 10 rows which are assigned to objTempList now in next step when i am doing foreach and adding more rows in objParentList its automaticaly reflecting in list objTempList and my loop is giving error message.

Answer 1

You should separate list instances to avoid this error

objTempList = objParentList.ToList();
foreach (var item in objTempList) 
{ 
   objChildList = objList.AsQueryable().Where(x => x._parentId == item.filedbid).ToList(); 
   foreach (var child in objChildList)
      objParentList.Add(child);       
}  

Answer 2

If you want to assign the contents of objParentList to objTempList without inadvertently modifying objTempList inside your foreach loop, then you need to create a new instance of of objParentList and assign that to objTempList.

That way, adding list items to the parent list inside of the loop will not throw an exception since you assigned a copy of the original to objTempList and not a reference. For example:

objTempList = new List<T>(objParentList);