在C語言中，雙向鏈表的插入操作可以分為三種情況：在鏈表的頭部插入節點、在鏈表的中間插入節點和在鏈表的尾部插入節點。以下是這三種情況的代碼示例：

1. 在鏈表的頭部插入節點：

void insertAtBeginning(Node **head_ref, int data) {
    Node *new_node = (Node *) malloc(sizeof(Node));
    new_node->data = data;
    new_node->prev = NULL;
    new_node->next = *head_ref;
    
    if (*head_ref != NULL) {
        (*head_ref)->prev = new_node;
    }
    
    *head_ref = new_node;
}

2. 在鏈表的中間插入節點：

void insertAfter(Node *prev_node, int data) {
    if (prev_node == NULL) {
        printf("The given previous node cannot be NULL");
        return;
    }

    Node *new_node = (Node *) malloc(sizeof(Node));
    new_node->data = data;
    new_node->prev = prev_node;
    new_node->next = prev_node->next;

    prev_node->next = new_node;

    if (new_node->next != NULL) {
        new_node->next->prev = new_node;
    }
}

3. 在鏈表的尾部插入節點：

void insertAtEnd(Node **head_ref, int data) {
    Node *new_node = (Node *) malloc(sizeof(Node));
    Node *last = *head_ref;
    
    new_node->data = data;
    new_node->next = NULL;
    
    if (*head_ref == NULL) {
        new_node->prev = NULL;
        *head_ref = new_node;
        return;
    }
    
    while (last->next != NULL) {
        last = last->next;
    }

    last->next = new_node;
    new_node->prev = last;
}

這些代碼示例展示了如何在雙向鏈表中插入節點。在實際應用中，根據具體情況選擇合適的插入方法。