Có 160+ tài liệu thuộc chủ đề "kĩ thuật lập trình"
tailieu.vn Xem trực tuyến Tải xuống
I'll show you how to use an object of the SqlTransaction class in this section.. The first INSERT statement will add a row to the Customers table, and the second one will add a row to the Orders table. Create a SqlTransaction object and start the transaction by calling the BeginTransaction() method of the SqlConnection object.. Create a SqlCommand object...
tailieu.vn Xem trực tuyến Tải xuống
A database trigger is a special kind of stored procedure that is run automatically by the database-or in trigger terms, fired-after a specified INSERT, UPDATE, or DELETE statement is run against a specified database table. For example, instead of performing an INSERT to add a row to the Products table, a trigger could raise an error if a product with...
tailieu.vn Xem trực tuyến Tải xuống
Introducing Visual Studio .NET. You can use Visual Studio .NET (VS .NET) to create console applications, as well as the following types of applications:. Windows Applications These take advantage of the visual controls offered by the Windows operating system, such as menus, buttons, and editable text boxes.. You'll learn about Windows programming in Chapter 6,. "Introducing Windows Applications and ADO.NET."....
tailieu.vn Xem trực tuyến Tải xuống
Issues Involved When Updating the Primary Key of a Parent Row. In this section, you'll learn about the issues involved when attempting to update the primary key in a parent DataTable, and then pushing the update to the underlying. The issues occur when the child database table already contains rows that use the primary key you want to change in...
tailieu.vn Xem trực tuyến Tải xuống
Storing information on the server gives you more control of the stored information, but since this consumes server resources, you need to be careful not to store too much. Storing Information on the Client. To store information on the client, you can use cookies or the Page object's ViewState property. A cookie is a name and value pair that is...
tailieu.vn Xem trực tuyến Tải xuống
NewCustomersRow() method of myDataTable MyDataSet.CustomersRow myDataRow = myDataTable.NewCustomersRow();. myDataTable.AddCustomersRow(myDataRow);. myDataRow = myDataTable.FindByCustomerID("J5COM");. foreach (MyDataSet.CustomersRow myDataRow2 in myDataTable.Rows). myDataTable.RemoveCustomersRow(myDataRow);
tailieu.vn Xem trực tuyến Tải xuống
In this section, you'll see the steps required to add, modify, and remove DataRow objects from a DataTable and then push those changes to the database. The examples in this section show how to add, modify, and delete rows in the Customers database table.. Note You'll find a complete program named AddModifyAndRemoveDataRows.cs in the ch11 directory that illustrates the use...
tailieu.vn Xem trực tuyến Tải xuống
step 3: use the Add() method through the Rows property. to add the new DataRow to the DataTable. Console.WriteLine("Calling myDataTable.Rows.Add()");. myDataTable.Rows.Add(myNewDataRow);. Console.WriteLine("myNewDataRow.RowState = ". myNewDataRow.RowState);. step 4: use the Update() method to push the new. row to the database. Console.WriteLine("Calling mySqlDataAdapter.Update()");. int numOfRows = mySqlDataAdapter.Update(myDataTable);. Console.WriteLine("numOfRows = ". You don't have to do this because the Update() method-like the Fill()...
tailieu.vn Xem trực tuyến Tải xuống
Notice that this program writes two XML files named nonNestedXmlFile.xml and nestedXmlFile.xml. The nonNestedXmlFile.xml contains the default non-nested rows, and nestedXmlFile.xml contains the nested rows after the. of a DataRelation to true causes the the child rows to be nested within the parent rows in the output XML. Console.WriteLine("Writing XML out to file nonNestedXmlFile.xml");. myDataSet.WriteXml("nonNestedXmlFile.xml");. (causes child rows to be...
tailieu.vn Xem trực tuyến Tải xuống
Before you can develop C# programs, you'll need to install either the .NET Software Development Kit (SDK) or VS .NET. You can download the .NET SDK at. http://msdn.microsoft.com/downloads (search for the Microsoft .NET Framework Software Development Kit). You can purchase a trial or full copy of VS .NET from Microsoft at http://msdn.microsoft.com/vstudio.. To install the .NET SDK, run the executable...
tailieu.vn Xem trực tuyến Tải xuống
Performing a SQL SELECT Statement and Storing the Rows Locally. In the example featured in this section, you'll see how to connect to the SQL Server Northwind database and perform a SQL SELECT statement to retrieve the CustomerID, CompanyName, ContactName, and Address columns for the first 10 rows from the Customers table. These rows are stored in a DataSet object.....
tailieu.vn Xem trực tuyến Tải xuống
The Fill() method then creates a DataTable in the DataSet with the specified name and runs the SELECT statement. The DataTable created in your DataSet is then populated with the rows retrieved by the SELECT statement.. to the Fill() method:. You can access these rows, even when disconnected from the database.. Step 11: Close the Database Connection. Close the database...
tailieu.vn Xem trực tuyến Tải xuống
You can therefore use very powerful filter expressions in your DataView. For example, you can use AND, OR, NOT, IN, LIKE, comparison operators, arithmetic operators, wildcard characters. Note For full details on how to use such filter expressions in your DataView objects, refer to the DataColumn .Expression property in the .NET online documentation.. When this code replaces the existing code...
tailieu.vn Xem trực tuyến Tải xuống
Reading a Column Value Using Strongly Typed DataSet Classes. A strongly typed DataSet object allows you read a column value using a property with the same name as the column. For example, to read the CustomerID of a column, you can use myDataRow.CustomerID rather than myDataRow["CustomerID". Another feature of a strongly typed DataSet is that when you work with it...
tailieu.vn Xem trực tuyến Tải xuống
As you learned in Chapter 2, a column defined as null can store a null value. A null value indicates that the column value is unknown. Let's consider an example of reading a null value from the database. performed a SELECT statement that retrieves the UnitPrice column for a row from the Products table, and that the UnitPrice column contains...
tailieu.vn Xem trực tuyến Tải xuống
You can read an individual column value in a row from a DataReader by passing the name of the column in square brackets. You can also specify the column you want to get by passing a numeric value in brackets. The first code snippet uses the column names to read the column values:. while (productsSqlDataReader.Read. Console.WriteLine(productsSqlDataReader["ProductID"]);. Console.WriteLine(productsSqlDataReader["ProductName"]);. Console.WriteLine(productsSqlDataReader["UnitPrice"]);. Console.WriteLine(productsSqlDataReader["Discontinued"]);. The...
tailieu.vn Xem trực tuyến Tải xuống
The ProductID column of the Products table is an identity column. In this section, you'll see how to insert a new row into to Products table and retrieve the new value generated by the database for the ProductID identity column.. Note You'll find a complete program named UsingIdentityColumn.cs in the ch11. In the examples, assume you have a DataTable named...
tailieu.vn Xem trực tuyến Tải xuống
Up to this point, you've retrieved column values from a DataReader only as generic objects of the System.Object class (such objects are often referred to as being of the C#. Note All classes in C# are derived from the System.Object class.. I'll rewrite the while loop shown in the example in the previous section to show how you store column...
tailieu.vn Xem trực tuyến Tải xuống
This might be useful if you have a very long transaction because if you make a mistake after you've set a savepoint, you don't have to roll back the transaction all the way to the start.. Inserts a row into the Customers table with a CustomerID of J8COM.. Sets a savepoint.. Inserts a row into the Orders table with a...
tailieu.vn Xem trực tuyến Tải xuống
Setting the Transaction Isolation Level. The transaction isolation level is the degree to which the changes made by one. Before I get into the details of the various transaction isolation levels, you need to understand the types of problems that might occur when current transactions attempt to access the same rows in a table. Dirty reads Transaction 1 updates a...