Watch Out When Setting the ID of a Master Page Dynamically

Published 17 years ago

It's not uncommon to set the ID of a Master Page in ASP.NET Programmatically. This is particularly useful when you have multiple master pages and want to have your CSS or JavaScript target specific control IDs in your code.

Without setting the ID property of the master page, a client side control ID may end up like this:

<input type="submit" name="ctl00$ContentPlaceHolder1$Button1" value="Button" 
id="ctl00_ContentPlaceHolder1_Button1" /> 

The ctl00 prefix on the id and name attributes represent the auto generated ID of the master page. Even if your page uses a different master, you may end up with the same prefix. Setting the server side ID of the master programmatically allows you to control the full control ID, making IDs predictable and thus more useable in client side code. For example, the following code in the code behind of the master page:

protected void Page_Init(object sender, EventArgs e)
{
  this.ID = "Master1";
}

<input type="submit" name="Master1$ContentPlaceHolder1$Button1" value="Button" 
id="Master1_ContentPlaceHolder1_Button1" /> 

This way you can assign a predictable master ID that your client side CSS and script can use.

If you use this trick, you have to be aware of when exactly to set the ID. Do it too late and you'll get in troubles.

Spaanjaars.Toolkit.ContentRating: Version 1.1

Published 17 years ago

Ever since I wrote the initial version of my ContentRating control back in 2006, I received a massive amount of feedback, both as comments below the article and as private e-mails. Not surprisingly, if you consider the article has been read over 19,000 times and has been rated 444 times (at the time of writing).

Besides getting a lot of "thank you's" from people who liked the control, I also got a lot of requests for a real-world example of a test site using the control. The test site that shipped with the control used fake data stored in ViewState to simulate a real backing store which obviously didn't cut it for a lot of people.

Also, a reader called vgt pointed out a bug in the control where an existing cookie would be overwritten by a new one one, effectively allowing you to vote for the previous item again.

Finally, I had a few requests of my own: I didn't like the default data source of 5 integers if you didn't supply a data source yourself. I also didn't like it that the control didn't raise an exception when you tried to data bind it without a valid data source.

So, enough reasons to fire up Visual Studio and get my hands dirty on some control fixing.

Fun With Extension Methods - Extending Object Part 1

Published 17 years ago

Some time ago I was showing a colleague how to enhance an object's Design Time capabilities (or actually Debug Time) by adding a DebuggerDisplayAttribute. I blogged about this attribute earlier, so I won't go into it again now. But what I do want to talk about is the way the attribute gets its data.

Fun With Extension Methods - Extending IDataRecord Part 2

Published 17 years ago

It's not uncommon that you have a method that accepts an object that implements the IDataRecord or IDataReader interface. It's also not uncommon that you cannot (fully) control the query that drives the IDataRecord. It could be the result of a SELECT * operation (bad idea) or it could be the results of a Stored Procedure for example. Especially in the latter case, it can be useful if you can check whether the IDataRecord contains a specific field. For example, you may want to check if the IDataRecord has a field called LastModified before you try to read and store this field in a local DateTime variable.

Unfortunately, the IDataRecord and IDataReader do not implement this behavior directly. However, it's easy to add with a simple extension method.

How to Check if Two Objects Look Like Each Other Without Using Equals

Published 17 years ago

A colleague (from Design IT) and I were discussing a simple way to check two instances of an object. We wanted to know if all the public properties on one instance were holding the same values as the one on the other instance. We wanted to use this knowledge in a few unit tests to simply check all public fields on an instance in one fell swoop.

Since we didn't want this exact behavior at run-time we couldn't override Equals and check all object's properties, so we had to look for a different solution.

Fun With Extension Methods - Extending IDataRecord

Published 17 years ago

For some reason, the IDataRecord interface and classes that implement it (DbDataReader, SqlDataReader and so on) only have Get* methods that accept the zero-based column index of a column in the result set. They don't allow you to get data by specifying a column name. As an example, consider the private FillDataRecord method to fill an e-mail address, as discussed in my article series about N-Layer development.

private static EmailAddress FillDataRecord(IDataRecord myDataRecord)
{
  EmailAddress myEmailAddress = new EmailAddress();
  myEmailAddress.Id = 
          myDataRecord.GetInt32(myDataRecord.GetOrdinal("Id"));
  myEmailAddress.Email = 
          myDataRecord.GetString(myDataRecord.GetOrdinal("Email"));
  // More fields here
  return myEmailAddress;
}		

The GetInt32 and GetString methods only have a single overload: one that accepts the zero-based index of the column. To satisfy these method signatures and make your code more readable at the same time, you can use GetOrdinal as shown in the previous example. Based on the column's name, GetOrdinal returns the column index. So, given the fact that the Id column is the first in the result set and Email the second, the previous piece of code equates to this:

myEmailAddress.Id = myDataRecord.GetInt32(0);
myEmailAddress.Email = myDataRecord.GetString(1);

Clearly, this is much more difficult to read and maintain than the previous example as you need to know the column indices and you should take great care not to mess with the column order in your select statements.

With a few extension methods, you can have the short syntax of the latter example, but still have readable code as the first example.

Fun With Extension Methods - Extending String to Provide a Better Split Method

Published 17 years ago

Do you feel that the standard Split implementation of the String class is a bit awkward to use? Do you keep forgetting you have to declare a char array for the separator? And do you often need to split on multiple characters, like \r\n to split on a line break? In that case, read on. A simple extension method might fix that for you.

Fun With Extension Methods - Extending Response.Redirect

Published 18 years ago

How often have you written code that redirects to another page and passes some local variables? You probably use string.Format to make your code easier to read. E.g.:

int categoryId;
// Code to assign a value to categoryId here
Response.Redirect(string.Format("SomePage.aspx?CatId={0}", categoryId.ToString()));

Have you ever wished there was an overload of the Redirect method that allowed you to omit the call to string.Format and simply let you write something like this:

int categoryId;
// Code to assign a value to categoryId here
Response.Redirect("SomePage.aspx?CatId={0}", categoryId.ToString());

This code makes it much easier to redirect to a page with a number of variables in the Query String. All you need to do is provide a composite format string as the new URL and a bunch of values that are used instead of the placeholders.

With Extension Methods - that come with .NET 3.5 - you can easily accomplish this yourself.

Custom Sorting with N-Layer Design Classes and the GridView

Published 18 years ago

Over the past couple of months I received a number of questions related to sorting with the classes from my N-Layer Design article series and the GridView. The good thing is: it isn't that hard; it's just that you need to know how to do it....

Building Layered Web Applications with Microsoft ASP.NET 2.0 - Part 3

Published 18 years ago

Update!! - I have written a new series on N-Layer design targeting ASP.NET 4.5 and Entity Framework 5. You can check out the new series here.

Update!! 12-24-2008 - I have written a new series on N-Layer design as a major follow up to this one. It builds on the foundation created in this first series, but digs much deeper into concepts like Validation, Sorting, Paging, Concurrency and Security. You can check out the new series here.

Update!! 04-25-2007 - There is now also a VB.NET version of the code available for download. You find the download at the end of this article. For more information about the translation, check out this blog post.

This is part three of the article series "Building Layered Web Applications" that shows you how to build N-Layer applications with Microsoft ASP.NET 2.0. These articles teach you how to design, build and use custom business objects in your web application. The target audience for this series are developers that are ready to make the switch from using SqlDataSource controls to ObjectDataSource controls with custom business objects. Experience with ASP.NET 2 and C# is necessary while some knowledge about object oriented design certainly helps.

Part one dealt with the design of the application: what business objects do you need to fulfill the requirements of the application. What should these objects be capable of and how do they look. How do these business objects interact with other parts of the system? Part two showed you how to code the classes that were designed in part one. You saw how to implement the data access methods and database code and how the various classes were able to work together. You also saw how to use the API to programmatically create contact persons and their contact data and save those in a database. However, writing explicit code to work with your business objects isn't always fun, and can be a cumbersome task.

Therefore, this article (part three) deals with using the business objects in a web application. You'll see how to use the ASP.NET controls like the GridView in conjunction with the business objects. You'll see how you can build pages that allow you to list, create, edit and delete your contact persons and their contact data, like e-mail addresses and phone numbers.

If you haven't read part one or two yet, you should really read them first, as this article uses many concepts that have been explained in part one and two. The entire series (including this current article) can be found here:

• Building Layered Web Applications with Microsoft ASP.NET 2.0 - Part 1
• Building Layered Web Applications with Microsoft ASP.NET 2.0 - Part 2
• Building Layered Web Applications with Microsoft ASP.NET 2.0 - Part 3

The article uses a SQL Server 2005 Express database which is easy to use in development scenarios. However, the downloads for this series also come with the T-SQL scripts to recreate the database in SQL Server 2000 or SQL Server 2005. You'll find the download link at the end of this article. Besides the forementioned SQL scripts and database, the download also contains the full source for the demo application in C#.