The c# method has error here :: PrintSinglyLinkedList(llist->head, "\n", textWriter);

The -> operator is not allowed c# (pointer only for c/c++).

Use another compiler.

The C# doesn't compile. Seeing this error even without my code:

Solution.cs(32,25): warning CS8625: Cannot convert null literal to non-nullable reference type.

compile failure in C# code

Here is my c++ solution you watch vide explanation here : https://youtu.be/COnfpdhOlN8

SinglyLinkedListNode* insertNodeAtHead(SinglyLinkedListNode* llist, int data) {
   SinglyLinkedListNode* new_node = new SinglyLinkedListNode(data);
   new_node -> next = llist;
   return new_node;
}