VC++ 实现连接到mongodb，和增删改查的例子代码

以下是一个连接到 MongoDB 数据库并进行增删改查操作的 VC++ 示例代码：

#include <iostream>
#include <mongoc.h>

int main(int argc, char* argv[])
{
    mongoc_client_t* client;
    mongoc_collection_t* collection;
    mongoc_cursor_t* cursor;
    bson_t* query;
    bson_t* doc;
    bson_error_t error;
    const char* uri_string = "mongodb://localhost:27017";
    const char* db_name = "mydb";
    const char* collection_name = "mycollection";

    mongoc_init();

    client = mongoc_client_new(uri_string);
    if (!client) {
        std::cout << "Failed to parse URI." << std::endl;
        return EXIT_FAILURE;
    }

    collection = mongoc_client_get_collection(client, db_name, collection_name);

    // insert document
    doc = bson_new();
    BSON_APPEND_UTF8(doc, "name", "John");
    BSON_APPEND_INT32(doc, "age", 25);
    if (!mongoc_collection_insert_one(collection, doc, NULL, NULL, &error)) {
        std::cout << "Insert failed: " << error.message << std::endl;
        return EXIT_FAILURE;
    }
    bson_destroy(doc);

    // find document
    query = bson_new();
    BSON_APPEND_UTF8(query, "name", "John");
    cursor = mongoc_collection_find_with_opts(collection, query, NULL, NULL);
    const bson_t* doc_result;
    while (mongoc_cursor_next(cursor, &doc_result)) {
        char* str = bson_as_json(doc_result, NULL);
        std::cout << str << std::endl;
        bson_free(str);
    }
    bson_destroy(query);
    mongoc_cursor_destroy(cursor);

    // update document
    query = bson_new();
    BSON_APPEND_UTF8(query, "name", "John");
    doc = bson_new();
    BSON_APPEND_UTF8(doc, "$set", "{ age: 26 }");
    if (!mongoc_collection_update_one(collection, query, doc, NULL, NULL, &error)) {
        std::cout << "Update failed: " << error.message << std::endl;
        return EXIT_FAILURE;
    }
    bson_destroy(query);
    bson_destroy(doc);

    // delete document
    query = bson_new();
    BSON_APPEND_UTF8(query, "name", "John");
    if (!mongoc_collection_delete_one(collection, query, NULL, &error)) {
        std::cout << "Delete failed: " << error.message << std::endl;
        return EXIT_FAILURE;
    }
    bson_destroy(query);

    mongoc_collection_destroy(collection);
    mongoc_client_destroy(client);
    mongoc_cleanup();

    return EXIT_SUCCESS;
}

需要注意的是，这里使用的是 MongoDB C Driver 进行操作，需要在项目中引入相应的库文件和头文件。另外，这里只是一个简单的示例，实际使用时还需要进行错误处理和资源释放等操作。