.NET/ASP.NET/C#/VB.NET PDF Document SDK

Thus, if you bind a button to this property and tie that binding to the button s enabled property, the button will automatically be disabled if you are currently looking at the first record As such, you can create, declaratively, a set of navigation buttons around a dataset This is exactly what is being done here Additionally, you want to implement an.

string trimmedLine = line.Trim(' ', '\t', ',');

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When querying for data, the database can perform calculations on the data before returning it. You saw such an example earlier in the chapter when COUNT(*) was used to count the number of family members for each lastname. There are a whole range of mathematical functions available in SQL. Some of the most common include SUM, MIN, and MAX, which are used to summarize the values of a column or to get the minimum or maximum value. These functions provide you with a powerful tool. When used in SELECT statements, it is possible to combine these functions with GROUP BY clauses to calculate results based on groups of rows. The results from these calculations can be combined using normal arithmetic operations such as +, -, *, and /. The following statement uses the SUM function, division, and COUNT(*) to calculate the average annual salary for each family: SELECT names.lastname, SUM(salaries.annual)/COUNT(*) AS 'Average', MIN(salaries.annual) AS 'Minimum', MAX(salaries.annual) AS 'Maximum' FROM names LEFT JOIN salaries ON names.id = salaries.id GROUP BY names.lastname Because you do a left join, the family members that do not have an income will be included in the COUNT(*), but not in the functions summarizing and picking out the minimum and maximum values. This means that the minimum salary for those named Doe stays at 900,

This overload of Trim uses the parameter array syntax, so we can specify the characters we want to trim as a simple parameter list. In this case, we tell it to trim spaces, tabs, and commas. Our output, then, looks like this:

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.

Of course, although the output is correct for this particular input, it isn t quite the same as the original Trim function it isn t removing all possible whitespace characters, just the ones we happened to remember to list. There are a surprising number of different characters that represent whitespace as well as your basic ordinary space, .NET recognizes a character for an en space (one the same width as the letter N), an em space (the same width as M), a thin space, and a hair space, to name just a few. There are more than 20 of the things! Example 10-79 shows a function that will trim all whitespace, plus any additional characters we specify.

but the average salary is calculated at 800. The complete results from the statement can be seen in the following table:

private static string TrimWhitespaceAnd( string inputString, params char[] characters)

{

}

It is with this problem in mind that Microsoft is attempting to bring the productivity of ASP.NET with Visual Studio 2005 to the Ajax space, and thus Atlas was born. In the next chapter, you ll be introduced to the wonderful world of Atlas, you will look at the architecture of it, you will learn how it allows you to use Visual Studio 2005 and ASP .NET 2.0 controls to generate client-side code from server-side controls, and you will see how this can give you the best of Ajax while avoiding the worst of it.

int start = 0; while (start < inputString.Length) { // If it is neither whitespace nor a character from our list // then we've hit the first non-trimmable character, so we can stop if (!char.IsWhiteSpace(inputString[start]) && !characters.Contains(inputString[start])) { break; } // Work forward a character start++; } // Work backwards from the end int end = inputString.Length 1; while (end >= start) { // If it is neither whitespace nor a character from our list // then we've hit the first non-trimmable character if (!char.IsWhiteSpace(inputString[end]) && !characters.Contains(inputString[end])) { break; } // Work back a character end--; } // Work out how long our string is for the // substring function int length = (end - start) + 1; if (length == inputString.Length) { // If we didn't trim anything, just return the // input string (don't create a new one return inputString; } // If the length is zero, then return the empty string if (length == 0) { return string.Empty; } return inputString.Substring(start, length);

It is easy to let the database perform lots of interesting functions on your data, which is both good and bad. The potentially negative consequence can be a heavier workload on a central server. The benefits are that less data is sent over the network and that the client code is less complex.