如何将C#镜像对象插入MongoDB

我是mongoDB的新手，我想将一个C#/SQL Server Windows应用程序转换为使用mongoDB作为其DB，我的程序正在从控制台捕获屏幕截图，并将其转换为C#Image对象，然后将其插入SQL Image类型，我的问题是如何在MongoDB中做到这一点，因为我的图像很小，我编写了一个小程序，从sql中读取并将其存储在MongoDB中（在MongoDB中将sql Image类型变为字符串），然后我从MongoDB中读取并尝试将其显示在图片框中，我在内存流中得到了一个错误，这就是错误：后面是我的程序代码。"参数无效。"

    public partial class Form1 : Form
{
    VideoEntities vid = new VideoEntities();
    public Form1()
    {
        InitializeComponent();
        connectToMongo();
    }
    public void connectToMongo()
    {
        Utilitys util = new Utilitys();
        var con = "mongodb://127.0.0.1";
        MongoClient client = new MongoClient(con);
        var db = client.GetDatabase("Video");
        ObjectResult<getFrame_Result> frame;
        List<getFrame_Result> frameList;
        frame = vid.getFrame(50604803);
        frameList = frame.ToList();
        string jsonStr = jsonStr = util.deserialze(frameList[0]);
        //            jsonStr = "{Frame:" + jsonStr + "}";
        jsonStr = jsonStr.Replace("[", "{");
        jsonStr = jsonStr.Replace("]", "}");
        var frameCollection = db.GetCollection<BsonDocument>("Frame");
        var oneFrame = BsonDocument.Parse(jsonStr);
        frameCollection.InsertOne(oneFrame);
        Byte[] data = new Byte[0];
        var collection = db.GetCollection<BsonDocument>("Frame");
        var filter = Builders<BsonDocument>.Filter.Eq("id", 50604803);
        var result = collection.Find(filter).ToList();
        string img = (string)result[0]["Frame"];
        data = Encoding.ASCII.GetBytes(img);
        MemoryStream mem = new MemoryStream(data);
        pictureBox.Image = Image.FromStream(mem);
    }
}

有人能帮忙吗？关于如何以正确的方式插入图像数据，使其成为二进制数据？

    public partial class Form1 : Form
{
    VideoEntities vid = new VideoEntities();
    public Form1()
    {
        InitializeComponent();
        connectToMongo();
    }
    public void connectToMongo()
    {
        Utilitys util = new Utilitys();
        var con = "mongodb://127.0.0.1";
        MongoClient client = new MongoClient(con);
        var db = client.GetDatabase("Video");
        ObjectResult<getFrame_Result> frame;
        List<getFrame_Result> frameList;
        frame = vid.getFrame(50604803);
        frameList = frame.ToList();
        **var frameCollection = db.GetCollection<getFrame_Result>("Frame");**
        frameCollection.InsertOne(frameList[0]);
        Byte[] data = new Byte[0];
        var collection = db.GetCollection<BsonDocument>("Frame");
        var filter = Builders<BsonDocument>.Filter.Eq("_id", 50604803);
        var result = collection.Find(filter).ToList();
        data = (Byte[]) result[0]["Frame"];
        MemoryStream mem = new MemoryStream(data);
        pictureBox.Image = Image.FromStream(mem);
    }
}