HTML5 Webcam Case: Create a self-signed certificate

Thanks to HTML5 which gives us the opportunity to use native HTML for some features. Without Flash or Silverlight we can use webcam. The new getUserMedia() function is used for capturing and video tag for displaying webcam content. 

Target

Assume that we have a web client in a kiosk and we want to run our webpage by opening a Chrome window. Creating a shortcut is easy part but you'll see Chrome asks for permission to enable webcam each time. This is a problem because someone has to allow webcam after a restart for example.

Solution

Running your website in HTTPS environment can solve this. Then Chrome will remember your preference for that page. If you allow webcam then each time it will gives permission automatically.

Self-signed Certificate

If you don't have an authorized certificate for the HTTPS then you can create a self-signed certificate in IIS. 

• Download & Install Internet Information Services (IIS) 6.0 Resource Kit Tools 
• Run the SelfSSL tool 
• Run command  SelfSSL /N:CN=computer-name /V:365  Parameters; CN is your server name and V is for validity days. If you don't specify site-id then its the first site by default.

You can enter big numbers for validity days like 1000 (which is 3+years) but for some security reasons Chrome will give warnings for that. In our case use smaller numbers like 365days.

Now you can see the certificate in IIS > Server Certificates section.
In IIS go to your Website > Bindings and select your certificate in HTTPS type.

Now your server is ready for HTTPS call and client can see your page's url in "https://your-server-name/..." format.

But still not finished. Chrome will say it the certificate is not verified. This is a self-signed certificate and we need to add it to Trusted Certificates in client side. See the next post 

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Performance Counters on ASP.NET

If you want to use performance counters on your ASP.NET page you can use  System.Diagnostics.PerformanceCounter class. Example below shows running inside a generic handler.

static System.Diagnostics.PerformanceCounter cpuUsage;

public void ProcessRequest(HttpContext context)
{
    context.Response.ContentType = "text/plain";
    if (cpuUsage == null)
    {
        cpuUsage = new System.Diagnostics.PerformanceCounter();
        cpuUsage.CategoryName = "Processor";
        cpuUsage.CounterName = "% Processor Time";
        cpuUsage.InstanceName = "_Total";
    }

    context.Response.Write(cpuUsage.NextValue());
}

When you test in Visual Studio you will see you can get CPU usage for every call (except first call, it is 0 for the first time). But when you deploy your code to the server probably you will see the error below.

Access to the registry key 'Global' is denied. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.UnauthorizedAccessException: Access to the registry key 'Global' is denied.

To solve this problem;

1. Check your application pool from the IIS website settings (basic or advance).


2. Go to "Application Pools" section. Right click and select "Advanced Settings".


3. Find "Identity".


4. Go to "Server Manager" > "Local Users and Groups" > "Groups". On the right pane right click to "Performance Monitor Users" > Properties.



5. Add user you saw in the 3rd step (Identity). If you saw "ApplicationPoolIdentity" in the "Identity" then type "IIS APPPool\[Pool name]". In our example pool name is "ASP.NET v4.0".

6. Restart IIS. Now you should see the performance counter page without error.

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Query samples on a self referenced table (Part-4)

In previous post we joined tables but there was a problem. We can not see "Help" menu which has not any sub menu. To solve the problem we will use Outer Join.

Linq

var menus = from t in Menus
  where t.MenuType==1
  join s in Menus on t.MenuID equals s.MenuParent into Subs
  from ss in Subs.DefaultIfEmpty()
  select new {
   TopMenu = t.Title,
   SubMenu = ss == null ? null : ss.Title
  };

Lambda

Menus
   .Where (t => (t.MenuType == 1))
   .GroupJoin (
      Menus, 
      t => (t.MenuID), 
      s => s.MenuParent, 
      (t, Subs) => 
         new  
         {
            t = t, 
            Subs = Subs
         }
   )
   .SelectMany (
      temp0 => temp0.Subs.DefaultIfEmpty (), 
      (temp0, ss) => 
         new  
         {
            TopMenu = temp0.t.Title, 
            SubMenu = (ss == null) ? null : ss.Title
         }
   )

SQL

DECLARE @p0 Int = 1

SELECT [t0].[Title] AS [TopMenu], 
    (CASE 
        WHEN [t2].[test] IS NULL THEN NULL
        ELSE CONVERT(NVarChar(MAX),[t2].[Title])
     END) AS [SubMenu]
FROM [Menu] AS [t0]
LEFT OUTER JOIN (
    SELECT 1 AS [test], [t1].[Title], [t1].[MenuParent]
    FROM [Menu] AS [t1]
    ) AS [t2] ON ([t0].[MenuID]) = [t2].[MenuParent]
WHERE [t0].[MenuType] = @p0

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Query samples on a self referenced table (Part-3)

In previous post we queried tables.

In this post we will join the tables. This will show Top Menu title and Sub Menu title in a row.

Linq

var menus = from t in Menus
  where t.MenuType == 1
  join s in Menus on t.MenuID equals s.MenuParent
  select new {
   TopMenu = t.Title,
   SubMenu = s.Title
  };

Lambda

Menus
   .Where (t => (t.MenuType == 1))
   .Join (
      Menus, 
      t => (Int32?)(t.MenuID), 
      s => s.MenuParent, 
      (t, s) => 
         new  
         {
            TopMenu = t.Title, 
            SubMenu = s.Title
         }
   )

SQL

DECLARE @p0 Int = 1

SELECT [t0].[Title] AS [TopMenu], [t1].[Title] AS [SubMenu]
FROM [Menu] AS [t0]
INNER JOIN [Menu] AS [t1] ON ([t0].[MenuID]) = [t1].[MenuParent]
WHERE [t0].[MenuType] = @p0

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Query samples on a self referenced table (Part-2)

In previous post we created a database table, filled it with sample data and saw some basic queries.

In this post we will query the table in { Menu.Title, IEnumerable<menu> } form. This will show Top menu title and sub menu items in a row.

Linq

var menus = from t in Menus 
 where t.MenuType==1 
 select new {
  t.Title,
  SubMenus = from s in Menus
  where t.MenuType==1 && t.MenuID==s.MenuParent
  select s
 };

Lambda

Menus
   .Where (t => (t.MenuType == 1))
   .Select (
      t => 
         new  
         {
            Title = t.Title, 
            SubMenus = Menus
               .Where (s => ((t.MenuType == 1) && ((Int32?)(t.MenuID) == s.MenuParent)))
         }
   )

SQL

DECLARE @p0 Int = 1
DECLARE @p1 Int = 1

SELECT [t0].[Title], [t1].[MenuID], [t1].[Title] AS [Title2], [t1].[Url], [t1].[MenuParent], [t1].[MenuType], (
    SELECT COUNT(*)
    FROM [Menu] AS [t2]
    WHERE ([t0].[MenuType] = @p0) AND (([t0].[MenuID]) = [t2].[MenuParent])
    ) AS [value]
FROM [Menu] AS [t0]
LEFT OUTER JOIN [Menu] AS [t1] ON ([t0].[MenuType] = @p0) AND (([t0].[MenuID]) = [t1].[MenuParent])
WHERE [t0].[MenuType] = @p1

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Query samples on a self referenced table (Part-1)

I will give you some query examples in Linq, Lambda Expression and SQL syntax.
Examples are build on one table that includes self referenced data. We will create a menu table on the database and fill it with some sample data. Some menu items are top menus and the others are subs. Sub menu items has a parent id which is referenced another menu item on the same table.

Step 1: Create menu table on SQL Server.

CREATE TABLE [dbo].Menu(
 [MenuID] [int] IDENTITY(1,1) NOT NULL,
 [Title] [nvarchar](50) NULL,
 [Url] [nvarchar](100) NULL,
 [MenuParent] [int] NULL, --If has parent fill this column with MenuID 
 [MenuType] [int] NULL --1: Top menu, 2:Sub menu
)

Step 2: Insert some data

INSERT INTO [dbo].[Menu] ([Title], [Url], [MenuParent], [MenuType]) VALUES ('Accounts', '.aspx', 0, 1) --ID=1

INSERT INTO [dbo].[Menu] ([Title], [Url], [MenuParent], [MenuType]) VALUES ('Users', '.aspx', 1, 2) --ID=2

INSERT INTO [dbo].[Menu] ([Title], [Url], [MenuParent], [MenuType]) VALUES ('Customers', '.aspx', 1, 2) --ID=3

INSERT INTO [dbo].[Menu] ([Title], [Url], [MenuParent], [MenuType]) VALUES ('Settings', '.aspx', 0, 1) --ID=4

INSERT INTO [dbo].[Menu] ([Title], [Url], [MenuParent], [MenuType]) VALUES ('App', '.aspx', 4, 2) --ID=5

INSERT INTO [dbo].[Menu] ([Title], [Url], [MenuParent], [MenuType]) VALUES ('Web', '.aspx', 4, 2) --ID=6

INSERT INTO [dbo].[Menu] ([Title], [Url], [MenuParent], [MenuType]) VALUES ('Service', '.aspx', 4, 2) --ID=7

INSERT INTO [dbo].[Menu] ([Title], [Url], [MenuParent], [MenuType]) VALUES ('Parameters', '.aspx', 0, 1) --ID=8

INSERT INTO [dbo].[Menu] ([Title], [Url], [MenuParent], [MenuType]) VALUES ('Account Type', '.aspx', 8, 2) --ID=9

INSERT INTO [dbo].[Menu] ([Title], [Url], [MenuParent], [MenuType]) VALUES ('Help', '.aspx', 0, 1) --ID=10

Step 3: Query table. In this example we will see some basic queries.

Basic Queries

Queries below selects top menus and sub menus.

Linq

var topMenus = from f in Menus where f.MenuType==1 select f;
var subMenus = from f in Menus where f.MenuType==2 select f;

Lambda

Menus
   .Where (f => (f.MenuType == 1))

Menus
   .Where (f => (f.MenuType == 2))

SQL

DECLARE @p0 Int = 1
SELECT [t0].[MenuID], [t0].[Title], [t0].[Url], [t0].[MenuParent], [t0].[MenuType]
FROM [Menu] AS [t0]
WHERE [t0].[MenuType] = @p0
GO

DECLARE @p1 Int = 2
SELECT [t0].[MenuID], [t0].[Title], [t0].[Url], [t0].[MenuParent], [t0].[MenuType]
FROM [Menu] AS [t0]
WHERE [t0].[MenuType] = @p1
GO

See Part-2 for the other queries.

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[Tips] Create numbers 0 to 23 query

Query below creates numbers 0 to 23.

WITH Hours(h) AS
(
    SELECT 0
    UNION ALL
    SELECT h+1 FROM Hours WHERE h < 23
)
SELECT h FROM Hours

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[Tips] Database convert to date

Oracle	SELECT to_date('01-JAN-2014', 'dd.MM.yyyy') FROM dual
SQL Server	SELECT CAST('01-JAN-2014' AS DATE)
SQL Server	SELECT CONVERT(DATE,'01/JAN/2014')

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[Tips] IE Mode

How to force IE mode to the latest version?

<meta http-equiv="X-UA-Compatible" content="IE=edge">

More info

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Working at home

Broadband networks, VPN, 3G, mobility, cloud... All these technologies provide people to communicate each other in a fast way. Video conferencing, online meetings can be easily done. Most of the people have computers, internet access, smart phones etc. But why we are still dependent to work at offices? 

Although technology adaptation is high we are still working traditionally. Face to face communication is preferred. Managers want to see their employees. Employees want to feel to be inside a community, use office facilities. People talk about flexible working conditions but most of the businesses are not ready to work at home.

Technology provides all the tools to work from the out of office. Microsoft has online meeting tools. But they don't say not to come to the office. All tools are just supplementary. If you are on vacation, traveling somewhere else etc. you can use technology. But you have to go to the office. Think Google. They have incredible office building. Everyone wants to work there.

Working at home may be a good idea but not ideal in the real world. So, companies should improve working place conditions to make people willing to be in the office.

Yahoo banned work at home and their reason is very clear. Yahoo's head of human resources, said:

To become the absolute best place to work, communication and collaboration will be important, so we need to be working side-by-side. That is why it is critical that we are all present in our offices. Some of the best decisions and insights come from hallway and cafeteria discussions, meeting new people, and impromptu team meetings. Speed and quality are often sacrificed when we work from home. We need to be one Yahoo!, and that starts with physically being together.

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