Selecting .NET Objects and Methods in .NET Connect Data Matrix 2d barcode in .NET Selecting .NET Objects and Methods

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Selecting .NET Objects and Methods using vs .net todraw data matrix ecc200 in web,windows application data matrix 100% Managed ADO.NET Provider .NET Managed Client Managed ADO.NET Provider .NET Managed Client 100% Managed .NET Provider .NET CLR Managed .NET Provider .NET CLR Database Vendor Client Libraries Unmanaged Code Figure 7-1. 100% managed data provider versus managed data provider Selecting .NET Objects and Methods The guidelines in Data Matrix for .NET this section will help you to optimize system performance when selecting and using ADO.NET objects and methods.

Avoiding the CommandBuilder Object Because of concurrency restrictions, the CommandBuilder often generates inefficient SQL statements. In most cases, you can code statements yourself that are more efficient than those the CommandBuilder generates. In addition, the CommandBuilder object generates statements at runtime.

Each time the DataAdapter.Update method is called, the CommandBuilder analyzes the contents of the result set and generates Insert/Update/Delete statements for the DataAdapter. When you explicitly specify Insert/Update/Delete statements, this extra processing step is eliminated.

. .NET Applications: Writing Good Code Performance Tip A Data Matrix 2d barcode for .NET lthough using a CommandBuilder object to generate SQL statements is tempting because it can save you time when coding an application that uses DataSets, this shortcut can impair performance..

Suppose you have an 8-column database table named employees that contains employee records. A CommandBuilder object would generate the following Update statement:. "UPDATE employees datamatrix 2d barcode for .NET SET empno = , ename = , job = , mgr = , hiredate = , sal = , comm = , dept = WHERE ( (empno = ) AND (ename = ) AND (job = ) AND ((mgr IS NULL and IS NULL) OR (mgr = )) AND (hiredate = ) AND (sal = ) AND ( (comm IS NULL AND IS NULL) OR (comm = )) AND (dept = )). If you know the u nderlying database schema and know that the empno column of the employees table is the primary key for the table, you can code the following Update statement, which is more efficient than the previous Update statement generated by the CommandBuilder:. UPDATE employees ECC200 for .NET SET empno = , ename = , job = , mgr = , hiredate = , sal = , comm = , dept = WHERE empno = . In this example, although we ve lost some concurrency control, we ve improved performance. Notice that in the first example, the Where clause compares every column value, which ensures the value hasn t changed since the data was retrieved. In the second example, the Update statement compares only the value of the empno column.

So before you implement this performance tip, you must decide how tolerant your database is to a lower level of concurrency. Choosing Between a DataReader and DataSet Object Which ADO.NET object should you use to retrieve the results of a SQL statement .

Selecting .NET Objects and Methods The DataReader object is optimized for retrieving large amounts of data at a fast speed. Data is read-only and can only be fetched in a forward-only order. Memory usage is minimal.

The DataSet object is a cache of data that represents the complete set of data results, including related tables, constraints, and relationships among the tables. It is, in effect, a locally cached database. You can modify the data in the DataSet and fetch data in any order.

Because the DataSet is disconnected from the database, any changes you make to the data in the DataSet must be explicitly synchronized with the data in the database. You also can create a DataSet from an XML stream or document, or you can serialize a DataSet to XML. Memory usage is high.

. Performance Tip I .net vs 2010 barcode data matrix f you need to retrieve large amounts of read-only data, a DataReader object always provides the best performance. Only use a DataSet object if you need to insert, update, or delete data, fetch data in any order, or work with XML.

Although the flexibility of a DataSet can benefit your application, it comes with the high cost in memory consumption.. Using GetXXX Meth ods to Fetch Data from a DataReader The .NET API provides the following methods of fetching data from a DataReader: Generic data type methods, such as GetValue() and GetValues() Specific data type methods, such as GetDateTime(), GetDecimal(), and. GetInt32(). When using a gene ric method such as GetValue() to fetch data from the DataReader, extra processing is required to convert the value data type to a reference data type, essentially wrapping the value data type with an object. This process is called boxing. When boxing occurs, memory is allocated from the managed heap on the database client to create an object for the reference data type, which can force a garbage collection to occur.

See .NET CLR, page 82, for more information about the impact garbage collection has on performance..

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