All the code examples are in Visual Basic. NET Chapter 1 introduces the concept of Oracle Database Extensions for. NET 2. NET, working with. NET data providers, connection pooling, system privileged connection, and single sign-on etc. Chapter 3 shows you several methods to retrieve data from an Oracle database. You will work with the core ODP. Chapter 4 is about inserting, updating, and deleting data in the database.
You will also learn about statement caching, array binding, working with offline data, implementing transactions, and handling errors and exceptions encountered during database work. Chapter 6 is completely dedicated to dealing with Large objects in Oracle. Chapter 8 deals with real-time application development scenarios like Oracle database change notifications, Asynchronous Application development, Web Application development using ASP.
It teaches you to connect to Oracle from the Visual Studio environment, retrieve Oracle information from Visual Studio, and work with database objects from Visual Studio. In the early days of databases, developers used to have knowledge on only one data access technology as they would usually concentrate on a single database. Later, numerous database products advanced quickly, leaving programmers in a confused state when selecting a particular data access methodology.
We now have several types of data access methodologies to develop applications. Choosing the best data access methodology is totally dependent on the type of application you are working on. The ADO. NET layer in the. NET architecture internally contains a few. NET data components or. NET data providers , which can be used to connect to and access any database. The data access through ADO.
NET is shown in the following figure along with other data access methodologies available prior to. NET :. Even though Microsoft designed its own. NET data providers, it has also opened its doors specification to the public and is encouraging other database companies to develop their own.
NET data providers. Microsoft made the data access model consistent among all of the. NET data providers and thus any. One of those is Oracle's ODP. NET, a. NET data provider that can connect to and access Oracle databases with tight integrity. The ODP. NET environment. It is one of the several data access methods to connect to and access Oracle databases. Oracle didn't simply stop giving support to Microsoft platform with only ODP.
Instead, it has extended its commitment for Microsoft. NET by adding Oracle database extensions for. Can't we access Oracle without ODP. Yes, we can. It is not compulsory for you to work with ODP.
As mentioned in the following section, we can still connect to and access Oracle using other alternative methods. But, in terms of features and performance, ODP. NET is your best choice for connecting. NET applications with Oracle database. Let us see how! I am limiting the discussion to only. NET applications or clients that are trying to access Oracle databases.
I will not be discussing application development prior to. Before discussing each of the above methodologies, let us understand their nature from the following figure:. Those are generic. NET data providers mainly targeted for most of the common data sources. If you plan to use either of those two. NET data providers, you are likely to face performance problems. In other words, ODBC. Figure 4 Selecting the ODP. NET is found under the Oracle. DataAccess component name. Select Oracle.
NET data provider known to your project. After adding references, it is standard practice to add Visual Basic Imports statements or C using statements. Technically, these statements are not required but they do allow you to refer to database objects without using lengthy, fully qualified names.
By convention, these statements appear at or near the top of a code file, before the namespace or class declaration. If you added the reference, Intellisense will help you complete the addition of an Imports or using statement as shown in Figure 5. Figure 5 Adding an Imports statement in Visual Basic.
An Oracle connection string is inseparable from Oracle names resolution. Suppose you had a database alias of OraDb defined in a tnsnames. The OraDb alias defines the database address connection information for the client. To use the OraDb alias defined in the tnsnames.
You can modify the connection string to obviate the need for the tnsnames. Simply replace the name of the alias with how it would be defined in a tnsnames. As you can see above, the username and password are embedded in the connection string in clear text. This is the simplest approach to creating a connection string. However, the clear text approach is undesirable from a security perspective. In particular, you must understand that compiled.
NET application code is only marginally more secure than the clear text source code files. It is very easy to decompile. Encryption is in fact the appropriate solution, but that subject would be a quite lengthy digression from our discussion here. Next, you must instantiate a connection object from the connection class. The connection string must be associated with the connection object.
Notice that the connection string is associated with the connection object by being passed through the object's constructor, which is overloaded. The constructor's other overload allows the following alternative syntax:. After associating a connection string with a connection object, use the Open method to make the actual connection.
Similar to the Connection object, it must be instantiated from its class and it has an overloaded constructor. In this sample, ODP. Using different overloads, the syntax can be structured slightly differently. The Command object has methods for executing the command text, which will be seen in the next section. Different methods are appropriate for different types of SQL commands.
Retrieving data from the database can be accomplished by instantiating an OracleDataReader object and using the ExecuteReader method, which returns an OracleDataReader object. Returned data is accessible by passing either the column name or zero-based column ordinal to the OracleDataReader.
There are typed accessors for returning. NET native data types and others for returning native Oracle data types, all of which are available in C , Visual Basic, or any other.
NET language. Zero-based ordinals are passed to the accessors to specify which column to return. In this simplified example, the returned value of DNAME is a string and is used to set the value of the label control's text property, which is also a string. NET runtime attempts to implicitly convert from one data type to another when the source and destination data types don't match. Sometimes the data types are incompatible and the implicit conversion fails, throwing an exception.
But even when it works, it's still better to use explicit data type conversions instead of implicit data type conversion. C is not as forgiving as Visual Basic on implicit conversions. You'll find yourself doing explicit conversions:. Either the connection object's Close or the Dispose method should be called to close the connection to the database.
The Dispose method calls the Close method. Closing and disposing. NET objects free up system resources, ensuring more efficient application performance, which is especially important under high load conditions. You can experiment with some of the concepts we've learned here in Lab 1 Retrieving Data from the Database and Lab 2 Adding Interactivity.
When an error occurs,. NET applications should gracefully handle the error and inform the user with a meaningful message. Try-Catch-Finally structured error handling is a part of.
Although this approach will gracefully capture any errors in attempting to get data from the database, it is not user friendly. For example, look at the following message displayed when the database is unavailable:. Figure 6 An ORA error caught and displayed to the user. A better solution is to add an additional Catchstatement to trap for the most common database errors and provide user-friendly messages.
Notice the two Catch statements in the code sample above. If there aren't any Oracle errors to catch, the first statement branch is skipped, leaving any other non-Oracle error to be caught by the second statement. Catch statements must be ordered in the code from most specific to most general.
After implementing the user-friendly exception handling code, the ORA error message appears as follows:. If you are not running 64bits VS you don't need 64bits ODBC datasource you just need to use the connection property at the top of VS to test your connection. I have covered general known issues with Oracle development in the thread below. Hope this helps. Hi, I have read the post that you mentioned above. So the issue is more of the fact that Visual Studio does not seem to be aware about the new.
NET installation. I am having the same issue. The content you requested has been removed. Ask a question.
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