如何遍历具有多个分支的树

Question

I'm working on an experimental TreeView where each TreeViewItem can either represent a condition, or a branch with an operator. This is to be parsed into SQL.

For example, the tree could have a branch with an "AND" or an "OR" operator, whose children would then be conditions. This is used to as to be able to generate the WHERE segment of an SQL statement, for example ((Name = 'Matt' AND AGE > 20) OR (Name = 'John' AND Age = 15)) AND Job = 'Student' .

How can I go about constructing that? What I've done so far is thought about placing a string,list<Condition> pair in a Tuple<> , where the string represents the branch operator (AND/OR), and the list represents the conditions contained within that branch.

However, since each branch can be split into a number of operator branches or conditions, it can get extremely complicated very quickly

Answer 1

You can use recursive function to parse the treeview from top, so each root note of the treeview is one SQL statement:

eg:

function code:

string getHead(TreeViewItem t)
            {
                string s = "";
                if (t.Items.Count == 0) //get the condition
                {
                    return s=t.Header.ToString(); //change this to your real getCondition function.
                }
                else
                {
                    for (int i = 0; i < t.Items.Count; i++ )
                    {
                        if(t.Items[i] is TreeViewItem) //Edit: only use treeviewitems not the button...
                        {
                          if (i == 0) // first note doesn't need the operator 
                          {
                            s += getHead(t.Items[0] as TreeViewItem);
                          }
                          else // only needs operator in between
                          {
                             s += (string.IsNullOrEmpty(getHead(t.Items[i] as TreeViewItem).Trim()) ? "" : (" " + t.Header + " " + getHead(t.Items[i] as TreeViewItem))); // only get real treeviewitem, not the one with two buttons and an empty header; change t.Header to your real getOperator function.

                          }
                        }                    
                    }
                    return string.Format("({0})",s); //group sub conditions
                }
            }

usage:

MessageBox.Show(getHead((treeView1.Items[0] as TreeViewItem)));

result:

Answer 2

In your tree view, aren't the last AND and OR supposed to be interchanged? I cannot get to the same parsed string you specified below with that view.

AND
    AND
         Job='Student'
         Age > 20
    AND
         OR
            Name='John'
            Name='Matt'
         Sex='Male'   

The last AND ands another OR condition and a single statement.

Not sure if this helps, but bison generates C code for bottom up parsing like this. You can give it a try.

e: conditional statement|
   e AND e|
   e OR e
;