An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key.

Create VIEW EmployeesView
AS
SELECT id,
       FirstName
FROM   Employees

using System.ComponentModel.DataAnnotations;

namespace EF_Sample04.Models
{
    [Table("EmployeesView")]
    public class EmployeesView
    {
        public int Id { set; get; }
        public string FirstName { set; get; }
    }
}

There is already an object named 'EmployeesView' in the database.

Database.SetInitializer<Sample04Context>(null);

Add-Migration Init -IgnoreChanges
Update-Database

using System.ComponentModel.DataAnnotations;
using System.Xml.Linq;

namespace EF_Sample04.Models
{
    public class MyXMLTable
    {
        public int Id { get; set; }

        [Column(TypeName = "xml")]
        public string XmlValue { get; set; }

        [NotMapped]
        public XElement XmlValueWrapper
        {
            get { return XElement.Parse(XmlValue); }
            set { XmlValue = value.ToString(); }
        }
    }
}

namespace EF_Sample04.Models
{
    public class ActivityType
    {
        public int UserId { set; get; }
        public int ActivityID { get; set; }
    }
}

using System.Data.Entity.ModelConfiguration;
using EF_Sample04.Models;

namespace EF_Sample04.Mappings
{
    public class ActivityTypeConfig : EntityTypeConfiguration<ActivityType>
    {
        public ActivityTypeConfig()
        {
            this.HasKey(x => new { x.ActivityID, x.UserId });
        }
    }
}

var activity1 = db.ActivityTypes.Find(4, 1);

using System.Collections.Generic;

namespace EF_Sample04.Models
{
    public class Employee
    {
        public int Id { set; get; }
        public string FirstName { get; set; }
        public string LastName { get; set; }

        //public int? ManagerID { get; set; }
        public virtual Employee Manager { get; set; }       
    }
}

using System.Data.Entity.ModelConfiguration;
using EF_Sample04.Models;

namespace EF_Sample04.Mappings
{
    public class EmployeeConfig : EntityTypeConfiguration<Employee>
    {
        public EmployeeConfig()
        {
            this.HasOptional(x => x.Manager)
                .WithMany()
                //.HasForeignKey(x => x.ManagerID)
                .WillCascadeOnDelete(false);
        }
    }
}

public class CustomNormalizer : ILookupNormalizer
    {
        public string NormalizeName(string key)
        {
            key = Normalize(key);
            key = key.ApplyCorrectYeKe()
                     .RemoveDiacritics()
                     .CleanUnderLines()
                     .RemovePunctuation();
            key = key.Trim().Replace(" ", "");
            return key;
        }
        public string NormalizeEmail(string key)
        {
            key = Normalize(key);
            key = fixGmailDots(key);
            return key;
        }
        public string Normalize(string key)
        {
            if (string.IsNullOrWhiteSpace(key))
            {
                return null;
            }

            key = key.Trim();
            key = key.ToUpperInvariant();
            return key;
        }

        private static string fixGmailDots(string email)
        {
            email = email.ToLowerInvariant().Trim();
            var emailParts = email.Split('@');
            var name = emailParts[0].Replace(".", string.Empty);

            var plusIndex = name.IndexOf("+", StringComparison.OrdinalIgnoreCase);
            if (plusIndex != -1)
            {
                name = name.Substring(0, plusIndex);
            }

            var emailDomain = emailParts[1];
            emailDomain = emailDomain.Replace("googlemail.com", "gmail.com");

            string[] domainsAllowedDots =
            {
                "gmail.com",
                "facebook.com"
            };

            var isFromDomainsAllowedDots = domainsAllowedDots.Any(domain => emailDomain.Equals(domain));
            return !isFromDomainsAllowedDots ? email : string.Format("{0}@{1}", name, emailDomain);
        }
    }

#region Assembly Microsoft.Extensions.Identity.Core, Version=3.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60
// C:\Users\kazemi\.nuget\packages\microsoft.extensions.identity.core\3.0.0-preview-18579-0056\lib\netstandard2.0\Microsoft.Extensions.Identity.Core.dll
#endregion

namespace Microsoft.AspNetCore.Identity
{
    //
    // Summary:
    //     Provides an abstraction for normalizing keys for lookup purposes.
    public interface ILookupNormalizer
    {
        //
        // Summary:
        //     Returns a normalized representation of the specified key.
        //
        // Parameters:
        //   key:
        //     The key to normalize.
        //
        // Returns:
        //     A normalized representation of the specified key.
        string Normalize(string key);
    }
}

public Article GetById(int id)
{
   return articles
         .Where(e => e.Id == id)
         .Include(x => x.Category)
         .Include(x => x.Tags) //پارامتر در نظر گرفته شده برای تولید کلید کش 
         .Cacheable(x => x.FirstOrDefault());
}

var collection = ['a', 1, /3/, {}];

collection[0];

collection.length

var numbers = [1, 2, 3];

_.each(numbers, function (num) {
    write(num);
});

var ary = [1, 5, 10];
var match = ary.find(item => item > 8);

var match = ary.findIndex(item => item > 8);

var ary = [1, 5, 10, 5, 6];
ary.fill('a', 2, 3)

// خروجی
[ 1, 5, "a", 5, 6 ]

[1, 2, 3, 4, 5].copyWithin(0, 3);

// [4, 5, 3, 4, 5]

var ary = new Array(1, 2);

var ary = new Array(1, 2, 3);

var ary = new Array(3);

var Ofary = Array.of(3);

var set = new Set([1, 2, 3]);
console.log(set.size); // logs 3

var set = new Set();
set.has(1); // false
set.add(1);
set.has(1); // true
set.clear();
set.has(1); // false
set.add(1);
set.add(2);
set.size;   // 2
set.delete(2);
set.size;   // 1

var set = new Set();
set.add('Vahid');
set.add('Sirwan');

var i = 0;
set.forEach(item => i++);
console.log(i);

var set = new Set();
set.add('Vahid');
set.add('Sirwan');

var i = 0;
for(let item of set) {
    i++;
}
console.log(i);

var map = new Map();
map.set('name', 'Sirwan');

map.get('name'); // Sirwan

var map = new Map();

map.set(1, true);
map.has("1"); // false

map.set("1", true);
map.has("1"); // true

var map = new Map([['name', 'Sirwan'], ['age', 27]]);
var i = 0;
map.forEach(function (value, key) {
    i++;
});
console.log(i); // log 2

for (var [key, value] of map) {
    i++;
}

using System;

public class ControlChars
{
   public static void Main()
   {
      int charsWritten = 0;

      for (int ctr = 0x00; ctr <= 0xFFFF; ctr++)
      {
         char ch = Convert.ToChar(ctr);
         if (char.IsControl(ch))
         {
            Console.Write(@"\U{0:X4}    ", ctr);
            charsWritten++;
            if (charsWritten % 6 == 0)
               Console.WriteLine();
         }     
      }  
   }
}
// The example displays the following output to the console: 
//       \U0000    \U0001    \U0002    \U0003    \U0004    \U0005 
//       \U0006    \U0007    \U0008    \U0009    \U000A    \U000B 
//       \U000C    \U000D    \U000E    \U000F    \U0010    \U0011 
//       \U0012    \U0013    \U0014    \U0015    \U0016    \U0017 
//       \U0018    \U0019    \U001A    \U001B    \U001C    \U001D 
//       \U001E    \U001F    \U007F    \U0080    \U0081    \U0082 
//       \U0083    \U0084    \U0085    \U0086    \U0087    \U0088 
//       \U0089    \U008A    \U008B    \U008C    \U008D    \U008E 
//       \U008F    \U0090    \U0091    \U0092    \U0093    \U0094 
//       \U0095    \U0096    \U0097    \U0098    \U0099    \U009A 
//       \U009B    \U009C    \U009D    \U009E    \U009F

• نصب پایتون  2.5 یا 2.6 یا 2.7 که فعلا در سایت آن، نسخه‌ی 2.7 در دسترس هست. توجه داشته باشید که هنوز برای نسخه‌ی 3 پایتون پشتیبانی صورت نگرفته است. 
  
• آخرین نسخه‌ی sdk را هم می‌توانید از این آدرس  به صورت zip و یا از این آدرس به صورت tar دانلود کنید و در صورتیکه دوست دارید به سورس آن دسترسی داشته باشید یا اینکه از سورس‌های مشارکت شده یا غیر رسمی استفاده کنید، از این صفحه آن را دریافت کنید.

(C:\Users\aym\Downloads\addon-sdk-1.17) C:\Users\aym\Downloads\addon-sdk-1.17\bin>

source bin/activate

bash bin/activate

(addon-sdk)~/mozilla/addon-sdk >

mkdir fxaddon
cd fxaddon
cfx init

* lib directory created
* data directory created
* test directory created
* doc directory created
* README.md written
* package.json written
* test/test-main.js written
* lib/main.js written
* doc/main.md written
Your sample add-on is now ready for testing:
try "cfx test" and then "cfx run". Have fun!"

{
  "name": "fxaddon",
  "title": "fxaddon",
  "id": "jid1-QfyqpNby9lTlcQ",
  "description": "a basic add-on",
  "author": "",
  "license": "MPL 2.0",
  "version": "0.1"
}

{
  "name": "dotnettips",
  "title": ".net Tips Updater",
  "id": "jid1-QfyqpNby9lTlcQ",
  "description": "This extension keeps you updated on current activities on dotnettips.info",
  "author": "yeganehaym@gmail.com",
  "license": "MPL 2.0",
  "version": "0.1"
}

var button= require('sdk/ui/button/action');

buttons.ActionButton({...});

var tgbutton = require('sdk/ui/button/toggle');
var panels = require("sdk/panel");
var self = require("sdk/self");

var button = tgbutton.ToggleButton({
  id: "updaterui",
  label: ".Net Updater",
  icon: {
    "16": "./icon-16.png",
    "32": "./icon-32.png",
    "64": "./icon-64.png"
  },
  onChange: handleChange
});

var panel = panels.Panel({
  contentURL: self.data.url("./popup.html"),
  onHide: handleHide
});

function handleChange(state) {
  if (state.checked) {
    panel.show({
      position: button
    });
  }
}

function handleHide() {
  button.state('window', {checked: false});
}

 tgbutton.ToggleButton

require('sdk/ui/button/toggle').ToggleButton

var contextMenu = require("sdk/context-menu");

var home = contextMenu.Item({
  label: "صفحه اصلی",
  data: "https://www.dntips.ir/"
});
var postsarchive = contextMenu.Item({
  label: "مطالب سایت",
  data: "https://www.dntips.ir/postsarchive"
});

var menuItem = contextMenu.Menu({
  label: "Open .Net Tips",
  context: contextMenu.PageContext(),
   items: [home, postsarchive],
  image: self.data.url("icon-16.png"),
  contentScript: 'self.on("click", function (node, data) {' +
                 '  window.location.href = data;' +
                 '});'
});

SelectorContext("img")

SelectorContext("img,a[href]")

var tabs = require("sdk/tabs");
var menuItem = contextMenu.Menu({
  label: "Open .Net Tips",
  context: contextMenu.PageContext(),
   items: [home, postsarchive],
  image: self.data.url("icon-16.png"),
  contentScript: 'self.on("click", function (node, data) {' +
                 '  self.postMessage(data);' +
                 '});',
 onMessage: function (data) {
     tabs.open(data);
  }
});

var Url="https://www.dntips.ir/search?term=";
var searchMenu = contextMenu.Item({
  label: "search for",
  context: [contextMenu.PredicateContext(checkText),contextMenu.SelectionContext()],
    image: self.data.url("icon-16.png"),
  contentScript: 'self.on("click", function () {' +
  '  var text = window.getSelection().toString();' +
                 '  if (text.length > 20)' +
                 '   text = text.substr(0, 20);' +
                 '  self.postMessage(text);'+
                '})',
onMessage: function (data) {
     tabs.open(Url+data);
  }
 
});

function checkText(data) {

       if(data.selectionText === null)
           return false;

       console.log('selectionText: ' + data.selectionText);

       //handle showing or hiding of menu items based on the text content.
       menuItemToggle(data.selectionText);

       return true;
};

function menuItemToggle(text){
var searchText="جست و جو برای ";
    searchMenu.label=searchText+text;

};

>db.COLLECTION_NAME.find()

>db.mycol.find().pretty()

>db.mycol.find().pretty()
{
   "_id": ObjectId(7df78ad8902c),
   "title": "MongoDB Overview", 
   "description": "MongoDB is no sql database",
   "by": "tutorials point",
   "url": "http://www.tutorialspoint.com",
   "tags": ["mongodb", "database", "NoSQL"],
   "likes": "100"
}
>

>db.mycol.find({key1:value1, key2:value2}).pretty()

>db.mycol.find({"by":"tutorials point","title": "MongoDB Overview"}).pretty()
{
   "_id": ObjectId(7df78ad8902c),
   "title": "MongoDB Overview", 
   "description": "MongoDB is no sql database",
   "by": "tutorials point",
   "url": "http://www.tutorialspoint.com",
   "tags": ["mongodb", "database", "NoSQL"],
   "likes": "100"
}
>

>db.mycol.find(
   {
      $or: [
     {key1: value1}, {key2:value2}
      ]
   }
).pretty()

>db.mycol.find({$or:[{"by":"tutorials point"},{"title": "MongoDB Overview"}]}).pretty()
{
   "_id": ObjectId(7df78ad8902c),
   "title": "MongoDB Overview", 
   "description": "MongoDB is no sql database",
   "by": "tutorials point",
   "url": "http://www.tutorialspoint.com",
   "tags": ["mongodb", "database", "NoSQL"],
   "likes": "100"
}
>

>db.mycol.find("likes": {$gt:10}, $or: [{"by": "tutorials point"}, {"title": "MongoDB Overview"}] }).pretty()
{
   "_id": ObjectId(7df78ad8902c),
   "title": "MongoDB Overview", 
   "description": "MongoDB is no sql database",
   "by": "tutorials point",
   "url": "http://www.tutorialspoint.com",
   "tags": ["mongodb", "database", "NoSQL"],
   "likes": "100"
}
>