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Ado.net
- 1. Introducing ADO.NET by Rajini K
- 6. SQL Managed Provider SQL Server Database ADO.NET Managed Provider ADO Managed Provider OLE DB Provider Database Your Application
- 21. DATA SET DataSet DataTable DataRelation DataRow DataColumn
Hinweis der Redaktion
- The DataReader was developed to get at data and in read-only forward-only fashion and provide the data as fast as possible to enable the developers as fast as possible. With the help of DataSet, it takes a snapshot of the data from database and storing this data offline for as long as necessary. When the end user using this copy of data he can persist the data and any changes to the data right back to data store.
- Among the above 6 core namespaces ADO.NET classes are divided into three categories: Disconnected : These classes provides basic structure of ADO.NET includes DataTable, etc., The objects of this class are capable of storing data without any dependency on specific data provider. Shared: Set of base classes for data providers and shared among all data providers. Includes DataSet, DataRow, DataTable, Constraint, etc., Data Providers: These classes are meant to work with different data sources. Performs all database management operations on a specific database. Eg: SqlClient data provider works only with SQL Server Database.
- ADO.NET ships with four database client namespaces. They are: System.Data.SqlClient System.Data.OracleClient System.Data.OleDb System.Data.Odbc. Within the .NET Framework data providers are light weight, creating minimal layer between the data source and code, increasing performance without scarifying functionality.
- The SqlConnection Properties the DataSource, Database and State are read-only properties to read database server , database name and state of connection respectively.
- Calling a stored procedure with a Command object is just assigning the stored procedure name to CommandText property of SqlCommand instance also setting the CommnadType property to CommandType.StoredProcedure value. Finally execute the one of previously stated method. The default ComandTimeout value is 30 seconds. The SqlRecord object contains only single returned row. When you begin transaction you can choose isolation level for commands executed within that transaction. This isolation levels specifies how changes made in one database session are viewed by another. These isolation levels are: ReadCommitted ReadUncomitted RepeatableRead Serializable ExecuteNonQuery() method is commonly user for UPDATE, INSERT or DELETE statements: This call will returns only the number of records effected. This call however can return results if you call a stored procedure that has output parameters.
- While calling ExecuteMethod (i.e., ExecuteReader ) if you provide CommandBehavior.CloseConnection the connection will be automatically closed whenever you reached to end of the result set. In between if you want to close the connection you can call the Close() method on your Connection object.
- While calling ExecuteMethod (i.e., ExecuteReader ) if you provide CommandBehavior.CloseConnection the connection will be automatically closed whenever you reached to end of the result set. In between if you want to close the connection you can call the Close() method on your Connection object.
- SelectCommand: Gets or sets an object of type SqlCommand . This command is automatically executed to fill a DataTable with the result set. InsertComand: Gets or sets an object of type SqlCommand . This command used automatically executed to insert a new record to the database. UpdateCommand: Gets or sets an object of type SqlCommand . This command used to update the existing record on database. DeleteCommand: Gets or sets an object of type SqlCommand . Used to delete an existing record on database.
- ParameterName: Gets or sets the name of the parameter SqlDbType: SQL server database type of the parameter value Size: Gets or sets the size of the parameter value. Direction: Gets or sets the direction of parameter such as input, output, or InputOutput . SourceColumn: Maps a column from a DataTable to the parameter. It enables you to execute multiple commands from SqlDataAdapter object and pick the correct parameter value from a DataTable column during the command execution. Value : Sets or gets the value provided by the parameter object. This value passed to the parameter defined in the command during the runtime.
- Here links means primary key and Foreign key relation ships etc., In the above DataColumn instance we have given column name to CustomerID . If we don’t give there will be auto-generated column name(1, 2, .., ) is assigned by runtime. DataRow versions are described as: Current : The value existing at present column within the column. If no edit has occurred since received from database then it will be same as original value. Default: The default value. Original: The value of the column when originally selected from database. Proposed: When changes are proposed for a row it is possible to retrieve this modified value. (In between BeginEdit() and EndEdit() methods). Better guideline regarding DataSet is don’t use DataSet object unless your project required to work with multiple DataTable objects and you need a container for those objects. If you are working with single table then just use DataTable object rather then DataSet .
- Better guideline regarding DataSet is don’t use DataSet object unless your project required to work with multiple DataTable objects and you need a container for those objects. If you are working with single table then just use DataTable object rather then DataSet . Server Explorer : In visual studio menu items select Data Generate Data Set;; It will creates Connection, adapter and xsd files. Using the DataAdapter : Open a connection Create a DataAdapter Finally Fill DataSet. To create DataSet programmatically: Define data column object Add DataColumn object to a DataTable Add DataTable object to a DataSet
- If you select data from database and populating it with adapter class runtime automatically creates the schema for your DataTable. It is also possible to create a DataTable programmatically. So creating schemas programmatically. Finally .NET framework also supports for using XML schemas to define a DataSet class, DataTable class and other classes. In the above relationships means Primary key and Foreign key relationship between the columns of different tables. The key difference between DataSet class and old style hierarchical Recordset object is in the way relationship is presented. In Recordset object the relationship was presented was a pseudo-column within the row. This column itself was a Recordset object. The below constrains are enforced within a DataSet class if the EnforcedConstraints property of the DataSet is true. Cascade: If the parent key has been updated copy new key value to all child records. If the parent record has been deleted then delete all the child records also. None: No action in child records whatsoever. This option leaves orphand rows within the child data table. SetDefault: Each child record affected has the foreign key column set to its default value if one has defined. SetNull: All child rows have the key column set to DBNull.
- If you are working on a single table just use DataTable instead of DataSet. If you are working with multiple table and you need container for those tables to make relations use DataSet . To load the data from DataReader to DataTable just call Load() method on DataTable . SqlDataReader myReader = cmd.ExecuteReader(..); DataTable myTable = new DataTable(); myTable.Load(myReader); In reverse if you want a reader from DataTable then use: DataTableReader myReader = myTable.CreateDataReader();
- From the early .Net have DataGrid control. But it have many draw backs such as can’t display images, can’t accommodate drop down control, or can’t lock columns etc., But with .NET DataGridView addresses all these problems. The AutoGenerateColumns property specifies whether the columns to create automatically when DataSource or DataMember is set. If you set to false you need to create all columns manually. The property DataSource gets or sets the data source for which the system displaying the data. The property DataMember gets or set the name of the list or table in the data sources for which DataGridView is displaying data.
- If you want to display combo box for any particular column then you need to create columns yourself by setting AutoGeneratedColumn property to false.
- All the Data Source Controls are derived from DataSourceControl class which it self derived from Control class and implements IDataSource and IListSoucre interfaces. You can use them as you would use any Web Server Control. All data source controls share basic set of core functionality. The SqlDataSource Control provides access to any data source that has ADO.NET data provider available. It has access to ODBC, OLEDB, SQL Server, Oracle, SQL Server CE providers. The SiteMapDataSource Control provides access to sitemap data for a web site that is stored by the sitemap provider. If your SQL query requires parameters to pass ASP.NET defines several parameter types: All are derived from Parameters class. ControlParameter CookieParameter FormParameter QueryStringParameter ( Used with SQL queries). ProfileParameter SessionParameter.
- With ASP.NET you can bind the data to a lot of databound controls: GridView, PageView, DrowDownList, ListBox, etc.,