IAC C# using GetAnnotIndex and GetAnnot Method

NOTE : There is an error in the code in above Q . Below is the correct code.

pDAnnot = (CAcroPDAnnot)pDPage.GetAnnot(annotIndex);

Coing back to  discussion , how can I do that ?

pDAnnot is not iterable in this specific case as it fetches single pDAnnot Object.

However, I can do a loop like this, but i see no upside to it.

for (int i = 0; i < pDPage.GetNumAnnots(); i++)
{
   pDAnnot = (CAcroPDAnnot)pDPage.GetAnnot(i);
   int j = pDPage.GetAnnotIndex(pDAnnot);
   // j & i will be same
}

Its like,

For getting annotation object (pDAnnot) you need to provide anootationIndex .

For getting anootationIndex , you need to provide ano\notation object(pDAnnot)

Am I missing something here ?