LINQ 分组依据，其中键是一个对象

>我有一个这个对象的数组：

public class WorkingOrderContract : BaseContract, IEquatable<WorkingOrderContract>
{
    public string Id { get; set; }
    public string Customer { get; set; }
    public string CategoryId { get; set; }
    public int ResourceId { get; set; }
    public virtual ResourceContract Resource { get; set; }
    public virtual CategoryContract Category { get; set; }
    public WorkingOrderEnum EWorkingOrder { get; set; }
    public TimeFlagEnum ETimeFlag { get; set; }
    public bool Equals(WorkingOrderContract other)
    {
        return this.Id == other.Id;
    }
}

由 JSON 文件动态加载。

我正在使用此代码进行分组，但它不起作用

var woListGrupped = this._workingOrderList.GroupBy(wo => wo.Category,
                               wo => wo,
                               (k, g) => new OdlByCategoryContract(k, g.ToList())
                               ).ToList();

我该怎么做？

var woListGrupped = this._workingOrderList.GroupBy(wo => wo.Category,
                               (k, g) => new OdlByCategoryContract(k, g.ToList())
                               ).ToList();