Simple .NET/ASP.NET PDF document editor web control SDK

A nice feature of the SQLite database engine is that the database can be created in memory. This means that the execution is very fast because no loading from and saving to disk is required. If you want the information to last beyond the termination of the application, you have to store it explicitly to a file or another database. By specifying the file name ":memory: ", as shown in the following code line, the database will be contained in memory: db.setDatabaseName( ":memory:" ); When a QSqlDatabase object represents a connection that is not longer used, you can close it using the close method. Any open connection is automatically closed by the QSqlDatabase destructor if left opened.

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or, if your C# source file has a using System; directive at the top, you can write this:

Rich controls: These are a special class of web controls that are complex in nature and generate large amounts of HTML and JavaScript An example of this is the Calendar control Validation controls: These controls validate input against a predetermined criteria, such as a telephone number or a ZIP code Should they fail validation, they encapsulate the logic to represent this on the web form Data controls: These encapsulate and display large amounts of data They include controls such as grids and lists, and they support advanced features such as using templates, editing, sorting, paginating, and filtering Navigation controls: These display site maps and allow users to navigate a site Login controls: These have built-in logic for forms authentication, providing a turnkey solution for authentication in your web sites WebPart controls: These build components for web portals running under Windows SharePoint Services.

Int32 answer = 42;

All of these are equivalent they produce exactly the same compiled output The last two are equivalent simply because of how namespaces work, but why does C# support a completely different set of aliases The answer is historical: C# was designed to be easy to learn for people who are familiar with the so-called C family of languages, which includes C, C++, Java, and JavaScript Most of the languages in this family use the same names for certain kinds of data types most use the name int to denote a conveniently sized integer, for example So C# is merely following suit it allows you to write code that looks like it would in other C-family languages By contrast, the NET Framework supports many different languages, so it takes the prosaic approach of giving these numeric data types descriptive names it calls a 32bit integer SystemInt32.

Since C# lets you use either naming style, opinion is divided on the matter of which you should use The C-family style (int, double, etc) seems to be the more popular Version 4 of the NET Framework introduces an extra integer type that works slightly differently from the rest: BigInteger It does not have a C-style name, so it s known only by its class library name Unlike all the other integer types, which occupy a fixed amount of memory that determines their range, a BigInteger can grow As the number it represents gets larger, it simply consumes more space The only theoretical limit on range is the amount of memory available, but in practice, the computational cost of working with vast numbers is likely to be the limiting factor Even simple arithmetic operations such as multiplication can become rather expensive with sufficiently vast numbers.

When passing an SQL query to a database, a QSqlQuery object is used to represent both the query and the results returned from the database engine Let s start by looking at a simple SELECT query Listing 13-3 shows a query being executed The SQL statement is simply passed to the exec method of a QSqlQuery object If the execution fails, the exec method returns false Upon failure, the lastError method of the query object contains more information about what went wrong Because you are dealing with a server being queried by a client application, it is not necessarily the SQL statement that is wrong it can also be connection failure, user authentication issues, or many other reasons Listing 13-3 Preparing and executing an SQL query if( !qryexec( "SELECT firstname, lastname FROM names " "WHERE lastname = 'Roe' ORDER BY firstname" ) ) qDebug() << qry.

For example, if you have two numbers each with 1 million decimal digits each number occupies more than 400 kilobytes of memory multiplying these together takes more than a minute on a reasonably well-specified computer BigInteger is useful for mathematical scenarios when you need to be able to work with very large numbers, but in more ordinary situations, int is the most popular integer type Integers are all very well for countable quantities, but what if you need the ability to represent something other than a whole number This is where floating-point types come in..