去重mongodb LIST

using MongoDB;
using DockSample.DB;
using MongoDB.Driver;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using WeifenLuo.WinFormsUI.Docking;
using MongoDB.Bson;

namespace DockSample
{
    public partial class Form2 : DockContent
    {
        public Form2()
        {
            InitializeComponent();
        }

        ////////////////////// workaround of RichTextbox control's bug:
        ////////////////////// If load file before the control showed, all the text format will be lost
        ////////////////////// re-load the file after it get showed.
        ////////////////////private bool m_resetText = true;
        ////////////////////protected override void OnPaint(PaintEventArgs e)
        ////////////////////{
        ////////////////////    base.OnPaint(e);
        ////////////////////    if (m_resetText)
        ////////////////////    {
        ////////////////////        m_resetText = false;

        ////////////////////    }
        ////////////////////}

        ////////////////////////protected override string GetPersistString()
        ////////////////////////{
        ////////////////////////    // Add extra information into the persist string for this document
        ////////////////////////    // so that it is available when deserialized.
        ////////////////////////    return GetType().ToString() + ",1123," + Text;
        ////////////////////////}

        ////////////////////private void menuItem2_Click(object sender, System.EventArgs e)
        ////////////////////{
        ////////////////////    MessageBox.Show("This is to demostrate menu item has been successfully merged into the main form. Form Text=" + Text);
        ////////////////////}

        ////////////////////private void menuItemCheckTest_Click(object sender, System.EventArgs e)
        ////////////////////{

        ////////////////////}

        ////////////////////protected override void OnTextChanged(EventArgs e)
        ////////////////////{
        ////////////////////    base.OnTextChanged(e);

        ////////////////////}

        private void button1_Click(object sender, EventArgs e)
        {
            usera u = new usera();
            u.cid = 10;
            u.name = "测试看看";
            WriteConcernResult s = MongoDBHelper.InsertOne("user", u);
            label1.Text = s.DocumentsAffected.ToString() + "------" + s.HasLastErrorMessage.ToString();//s.HasLastErrorMessage=false既是表示操作成功！
        }

        private void button2_Click(object sender, EventArgs e)
        {
            IMongoQuery query = MongoDB.Driver.Builders.Query.EQ("cid", 9);
           // usera u = MongoDBHelper.GetOne<usera>("user", query);
            IEnumerable<usera> u = MongoDBHelper.GetAll<usera>("user").Distinct<usera>(new ModelComparer());

            //usera u = MongoDBHelper.GetOne<usera>("user", "555993c18825b905c8879edc");
            //label1.Text = u.cid.ToString() + "---" + u.name;

            foreach(usera ua in u)
            {
                richTextBox1.AppendText(ua.cid.ToString() + "--" + ua.name + "\r\n");
            }
        }

        private void button3_Click(object sender, EventArgs e)
        {
            MongoDBHelper.DeleteAll("user");

        }

    }

    public class usera
    {
        public ObjectId id { get; set; }
        public int cid { get; set; }

        public string name { get; set; }
    }

    public class ModelComparer : IEqualityComparer<usera>
    {
        public bool Equals(usera x, usera y)
        {
            return x.name.ToUpper() == y.name.ToUpper();
        }
        public int GetHashCode(usera obj)
        {
            return obj.name.ToUpper().GetHashCode();
        }
    }
}