ASP.NET Web PDF Document Viewer/Editor Control Library

Not only will this fix our blank-line problem, but it will also remove any whitespace that the user has left at the start and end of the line.

You often (but not always) want to trim whitespace from the beginning and/or end of a piece of text; especially user-provided text. When storing data in a SQL database, for example, it is frequently desirable to trim this whitespace. With that in mind, the framework provides us with the Trim, TrimStart, and TrimEnd methods. Example 10-77 uses Trim to remove the whitespace at the start and end of every line.

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However, in Atlas parlance the two are both treated as <textBox> controls, which is more logical: <textBox targetElement="descriptionField"> <bindings> <binding dataPath="Description" property="text" direction="InOut"/> </bindings> </textBox> Now you can define the buttons that allow you to navigate These show some interesting functionality Let s first look at the Move Previous button (labeled < in the application): <button targetElement="previousButton"> <bindings> <binding dataContext="detailsView" dataPath="canMovePrevious" property="enabled"/> </bindings> <click> <invokeMethod target="detailsView" method="movePrevious" /> </click> </button> When the <itemView> control has a set of records loaded in it (using its data property), it exposes a number of properties for navigating that data One of these properties is canMovePrevious, which is false if you are currently looking at the first record in the dataset and true otherwise.

foreach (string line in strings) { if (line != null) { string trimmedLine = line.Trim(); if (trimmedLine.Length != 0) { output.AppendLine(trimmedLine); } else { System.Diagnostics.Debug.WriteLine( "Found a blank line (after trimming)"); } } else { System.Diagnostics.Debug.WriteLine("Found a null line"); } }

To get all the rows from the names table, replace JOIN with LEFT JOIN. All the rows are returned from the first table (the one on the left in the statement). The resulting statement is this: SELECT names.firstname, names.lastname, salaries.annual FROM names LEFT JOIN salaries ON names.id = salaries.id The rows not represented in the salaries table get the value NULL. The result from the query can be seen in the following table:

Notice how we re trimming the line once, and storing a reference to the result in a variable, then using that trimmed string in our subsequent tests. Because we re calling a method on our string instance, we need to test it for nullness before we do that, or we ll get a null reference exception. This means that we don t need to call IsNullOr Empty in our later test. We know that it cannot be null. Instead, we do a quick test for emptiness. It turns out that the most efficient way to do this is not to compare against String.Empty but to check the Length of our string. If we build and run this, we see the following output:

To be, or not to be--that is the question: Whether 'tis nobler in the mind to suffer, The slings and arrows of outrageous fortune , Or to take arms against a sea of troubles, And by opposing end them.

And in the output window:

Found Found Found Found Found Found Found Found Found a a a a a a a a a blank line null line blank line blank line blank line blank line blank line blank line blank line (after trimming) (after (after (after (after (after (after (after trimming) trimming) trimming) trimming) trimming) trimming) trimming)

When working with databases with several tables, it is important to have a normalized structure. Under normal circumstances, no information should appear more than once. An example of the opposite is if the salaries table contains the lastname and id. In such a case, changing the lastname requires two UPDATE calls. The tables used this far are pretty simple, but try to remember to keep data in only one place (which might sometimes require additional id columns just to tie things together). This is a time well spent because it makes the structure easier to work with. This introduction to SQL only scratches the surface of database design and join statements. There are many more aspects to take into account before implementing a complex database, and there are numerous other ways of joining tables and creating relationships. Some of them are standardized, and others are very dependent on the database server you are using. Before implementing any complex database design I suggest that you consult you database server s documentation as well as books focusing on the topic.

You ll notice that Trim has successfully removed all the whitespace at the beginning and end of each line, both spaces and tab characters, but left the whitespace in the middle of the line alone.

us to specify the array of characters we want to trim from the beginning or end of the line. We could use this to get rid of those spurious commas, too, using the code in Example 10-78.