One-to-one foreign key relationship in Entity Framework

This site seems to have useful contents for those who want to re-visit their knowledge about Entity Framework.

The example on "One-to-One or One-to-Zero Foreign Key Relationship" was especially useful.

Take a look.

Site Url = http://www.EntityFrameworkTutorial.net

Genenrate full Url (absolute Url) using C# in ASP.NET MVC

A quick way to generate full Url (absolute Url) in ASP.NET MVC:

Url.Action("Details", "Product", new { id = p.ProductID}, Request.Url.Scheme)

If without id, simply use null in the parameter.

Url.Action("Details", "Product", null, Request.Url.Scheme)

Stop screensaver autolock

A quick VBScript could be useful in keeping computer active without screensaver automatically taking over. For security policies, most companies have automatic screensaver or session lock in place based on user inactivity. For those of us who need to keep the system monitor PC on all the time, this script could be useful. It basically sends escape key stroke once a minute for the duration of time you specify.

Dim shell, minutes, minuteCount
minutes = 300

Set shell = CreateObject("WScript.Shell")
minuteCount = 0
For minuteCount = 0 To minutes
  shell.SendKeys "{ESC}"
  minuteCount = minuteCount + 1
  WScript.Sleep(60000) 
Next

Just don't forget to lock the computer when you step away from the computer.
To stop the script, close "WScript.exe" in Task Manager or logout from Windows.

Custom Error Page in ASP.NET MVC

Setting up custom error page for 400 (bad request), 401 (unauthorized), 403 (forbidden), 404 (not found), 500 (internal server error) seemed like a web.config task as simple as specifying

    
<system.web>
    <customErrors mode="On" redirectMode="ResponseRedirect"  >
      <error statusCode="400" redirect="~/CustomError/BadRequest"/>
      <error statusCode="401" redirect="~/CustomError/Unauthorized" />
      <error statusCode="404" redirect="~/CustomError/NotFound"  />
      <error statusCode="403" redirect="~/CustomError/Forbidden"/>
      <error statusCode="500" redirect="~/CustomError/InternalServerError"/>
    </customErrors>
</system.web>

However, the above may not allow our custom error pages to handle certain cases.

For example, the default IIS 404 error page, not my custom error page, will handle 404 for url that is not understood by my MVC application's routing rule (i.e., http://localhost/MyApp/a/b/c/d/e/f).

It may be easier to use <httpErrors> under <system.webServer> rather than <customErrors> in <system .web>. The above can be converted to below. Note that we cannot use ~/ in the path attribute. <system.webServer> is IIS-level override for customError handling in this case. So remove the above and try something like the following.

<system.webServer>
  <httpErrors errorMode="Custom" existingResponse="Replace">      
    <remove statusCode="400" />
    <remove statusCode="401" />
    <remove statusCode="403" />
    <remove statusCode="404" />
    <remove statusCode="500" />
    <error statusCode="400" path="/MyApp/CustomError/BadRequest" responseMode="ExecuteURL"/>
    <error statusCode="401" path="/MyApp/CustomError/Unauthorized" responseMode="ExecuteURL"/>
    <error statusCode="403" path="/MyApp/CustomError/Forbidden" responseMode="ExecuteURL"/> 
    <error statusCode="404" path="/MyApp/CustomError/NotFound" responseMode="ExecuteURL"/>
    <error statusCode="500" path="/MyApp/CustomError/InternalServerError" responseMode="ExecuteURL"/>
  </httpErrors>
</system.webServer>

Below is the Controller

public class CustomErrorController : Controller
{
 public ActionResult BadRequest()
 {
  Response.StatusCode = 400;
  ViewBag.ErrorCode = "400";
  ViewBag.ErrorTitle = "400 Error - Bad Request";
  ViewBag.ErrorMessage = 
   "The resource you tried to access appears to be incomplete.\n" + 
   "Please check your URL and try again.";
  return View("Error");
 }
 public ActionResult Unauthorized()
 {
  Response.StatusCode = 401;
  ViewBag.ErrorCode = "401";
  ViewBag.ErrorTitle = "401 Error - Unauthorized";
  ViewBag.ErrorMessage = 
   "The resource you tried to access appears to require a user permission.\n" + 
   "Please re-launch the browser and try again.";
  return View("Error");
 }
 public ActionResult Forbidden()
 {
  Response.StatusCode = 403;
  ViewBag.ErrorCode = "403";
  ViewBag.ErrorTitle = "403 Error - Forbidden: Access is denied";
  ViewBag.ErrorMessage = 
   "The resource you tried to access is not allowed. \n" + 
   "Please check your URL and try again.";
  return View("Error");
 }
 public ActionResult NotFound()
 {
  Response.StatusCode = 404;
  ViewBag.ErrorCode = "404";
  ViewBag.ErrorTitle = "404 Error - Resource Not Found";
  ViewBag.ErrorMessage = 
   "The resource you tried to access was not found.\n" + 
   "Please check your URL and try again.";
  return View("Error");
 }
 public ActionResult InternalServerError()
 {
  Response.StatusCode = 500;
  ViewBag.ErrorCode = "500";
  ViewBag.ErrorTitle = "500 Error - Internal Server Error";
  ViewBag.ErrorMessage = 
   "An error occurred while system tried to process your request.\n" + 
   "Try again, and if problem persists contact system administrator.";
  return View("Error");
 }
}

And the View

@{
    ViewBag.Title = ViewBag.Title;
}

<div style="text-align: center;">
    <div style="font-size: 10em; color:#ccc; font-weight: bold; ">
        @ViewBag.ErrorCode
    </div>

    <h2>
        @ViewBag.ErrorTitle
    </h2>

    <h3 style="white-space: pre-wrap; word-wrap: break-word;">@ViewBag.ErrorMessage</h3>

    <h4>
        <a href="javascript:void(0);" onclick="javascript: history.go(-1);">Back</a>
    </h4>
</div>

And this is the custom 404 page.

Format <td> to handle linefeed and wrap long text in a table

When a table cell needs to properly display texts with linefeed and really long text with no whitespace (i.e., long URL), try the following styles.

<table style="table-layout: fixed">
  <tbody>
    <tr>
      <td>Some Links</td>
      <td style="white-space: pre-wrap; word-wrap: break-word">
        ...
      </td>
    </tr>
  </tbody>
</table>

Below is a problematic example of table cell display. The long URL text, which has no whitespace character stretches the table's width beyond the specified table width of 400px.

<table style="width: 400px; border: 1px solid white; color: white">
  <tbody>
    <tr>
      <td style="width: 100px; border: 1px solid white; vertical-align: top; ">Some Links</td>
      <td style="border: 1px solid white;" >Link Example: 
        https://www.google.com/maps/@33.7338729,-117.8530829,3a,75y,304h,90t/data=!3m7!1e1!3m5!1suAg9o6LKzX3</td">
    </tr>
  </tbody>
</table>

Some Links

Link Example: https://www.google.com/maps/@33.7338729,-117.8530829,3a,75y,304h,90t/data=!3m7!1e1!3m5!1suAg9o6LKzX3

Below is better way to display the content with proper line-feed in order to keep the specified table width of 400px;

<table style="width: 400px; border: 1px solid white; color: white; table-layout: fixed;">
  <tbody>
    <tr>
      <td style="width: 100px; border: 1px solid white; vertical-align: top; ">Some Links</td>
        <td style="border: 1px solid white; 
          white-space: pre-wrap; word-wrap: break-word;" >Link Example:
https://www.google.com/maps/@33.7338729,-117.8530829,3a,75y,304h,90t/data=!3m7!1e1!3m5!1suAg9o6LKzX3</td>
    </tr>
  </tbody>
</table>

Some Links

Link Example: https://www.google.com/maps/@33.7338729,-117.8530829,3a,75y,304h,90t/data=!3m7!1e1!3m5!1suAg9o6LKzX3