Recursive Function Calls Throw StackOverFlowException

Question

I've to call a function recursively. But after a moment it throws StackOverFlowException. When I used Invoke(new Action(Start)) method, it throws same exception but not in a long moment, this is shorter than the previous one.

How can I overcome this problem?

Example Code:

private void Start()
 {
 // run select query
 mysql(selectQueryString.ToString());
 msdr = mysql();
// is finished
 if (!msdr.HasRows)
 {
 this.Finish();
 return;
 }
 // get mysql fields
 string[] mysqlFields = Common.GetFields(ref msdr);
 while (msdr.Read())
 {
 // set lastSelectID
 lastSelectID = Convert.ToInt32(msdr[idFieldName].ToString());
 // fill mssql stored procedure parameters
 for (int i = 0; i < matchTable.Count; i++)
 {
 string valueToAdd = Common.ConvertToEqualivantString(matchTable[i].Type, matchTable[i].Value, ref msdr, ref id, matchTable[i].Parameters);
 sql.Ekle(matchTable[i].Key, valueToAdd);
 }
 // execute adding operation
 lastInsertID = (int)sql(false);
 // update status bar
 this.UpdateStatusBar();
// update menues
 this.UpdateMenues();
 // increment id for "{id}" statement
 id++;
 }
// close data reader
 msdr.Close();
 msdr.Dispose();
 mysql.DisposeCommand();
// increment select limit
 selectQueryString.LimitFirst += selectQueryString.LimitLast;
 // call itself until finish
 this.Start();
 }

• Simon Whitehead: How many recursions are you expecting? Of course you'll eventually blow the stack.. You have no condition that stops the recursions.. it continues going forever as far as I can see..
• user743382: @SimonWhitehead The terminating condition is there at the top of the method, with an early return. But the condition doesn't look like a good one to me. Edit: and I was wrong about that, mysql() returns something different thing every time.
• Mesut: // increment select limit selectQueryString.LimitFirst += selectQueryString.LimitLast
• Fede: Dude, for Christ's sake, use an ORM. Stop trying to reinvent the wheel. Remove all this horrible code from your code behind. Learn and use a proper architecture and design pattern such as MVC or MVVM, instead of mashing all together UI, Business Logic and Data Access.
• RBarryYoung: Why are you recursing at all?!? The correct way to do this is to loop until there are no more rows, not recurse until done and hope that you have enough stack. The way to fix this is to change your recursion into an outer loop.

Answer 1

When the last statement in a function is the call to the function itself, you have tail-recursion. While there are languages that optimize tail-recursion to avoid a stack overflow exception, C# is not one of them.

Recursion is not a good pattern for data that can be of an arbitrary length. Simply replace recursion by a while loop:

private void Start()
{
 while(true) {
 // run select query
 mysql(selectQueryString.ToString());
 msdr = mysql();
 // is finished
 if (!msdr.HasRows)
 {
 this.Finish();
 break;
 }
 // rest of your code..
 }
}

• Mike Mertsock: +1 for mentioning that the C# compiler doesn't do tail recursion, and its relevance to this question.
• tia: Better say that C# does not guarantee that tail call will work without stack overflow. At least on x64, tail call does work. stackoverflow.com/questions/15864670/generate-tail-call-opcode

Answer 2

You must always have the breaking condition in the recursion. If you need the best sample to implement the recursion in effective way then you can follow this approach recursion example