在列表中添加新值用新对象c＃覆盖列表中的先前值

Question

我实质上是想将多个项目添加到列表中，但最后所有项目的值都等于最后一个项目。

model.DocumentShapeModel = JsonConvert.DeserializeObject<List<DocumentShapeModel>>(model.Shapes);
var documentShapeModel = model.DocumentShapeModel.ToList();

for (int j = 0; j < documentShapeModel.Count; j++)
{
    if (documentShapeModel[j].userId.Contains("1111"))
        documentShapeModel[j].userId = string.Empty;
    string[] signerList = documentShapeModel[j].userId.Split(",");
    if (signerList.Length > 1)
    {
        var signerIdList = new List<string>();
        signerIdList = model.SignerIds.ToList();
        var itemToRemove = model.DocumentShapeModel.SingleOrDefault(r => r.userId == documentShapeModel[j].userId);
        model.DocumentShapeModel.Remove(itemToRemove);


        var shapeList = new List<DocumentShapeModel>();
        for (int i = 0; i < signerList.Length; i++)
        {
            var shapes = new DocumentShapeModel();
            shapes = documentShapeModel[j];
            shapes.userId = signerList[i].Trim();
            model.DocumentShapeModel.Append(shapes);

            signerIdList.Add(signerList[i].Trim());
        }
        model.SignerIds = signerIdList.ToArray();
    }
}