Searching for "DataTable"

Q:

You use Microsoft Visual Studio 2010 and Microsoft .NET Framework 4 to create an
application. The application connects to a Microsoft SQL Server database. The application has two DataTable objects that reference the Customers and Orders tables in the database. The application contains the following code segment. (Line numbers are included for reference only.)


01DataSet customerOrders = new DataSet();
02customerOrders.EnforceConstraints = true;
03ForeignKeyConstraint ordersFK = new ForeignKeyConstraint("ordersFK",
04customerOrders.Tables["Customers"].Columns["CustomerID"],
05customerOrders.Tables["Orders"].Columns["CustomerID"]);
06
07customerOrders.Tables["Orders"].Constraints.Add(ordersFK);


You need to ensure that an exception is thrown when you attempt to delete Customer records that have related Order records. Which code segment should you insert at line 06?

A) ordersFK.DeleteRule = Rule.SetNull; B) ordersFK.DeleteRule = Rule.None;
C) ordersFK.DeleteRule = Rule.SetDefault; D) ordersFK.DeleteRule = Rule.Cascade;
 
Answer & Explanation Answer: B) ordersFK.DeleteRule = Rule.None;

Explanation:
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Q:

You ASP.NET application manages order entry data by using a DataSet object named EXorderEntry. The EXorderEntry object includes two DataTable objects named orderNames and OrderDetails. A ForeignKeyConstraint object named orderDetailsKey is defined between the two DataTable objects.


You attempt to delete a row in orderNames while there are related rows in OrderDetails, and an exception is generated.What is the most likely cause of the problem?

A) The current value of OrderDetails.KeyDeleteRule is Rule.Cascade. B) The current value of OrderDetails.KeyDeleteRule is Rule.SetNull.
C) The current value of OrderDetails.KeyDeleteRule is Rule.SetDefault. D) The current value of OrderDetails.KeyDeleteRule is Rule.None.
 
Answer & Explanation Answer: D) The current value of OrderDetails.KeyDeleteRule is Rule.None.

Explanation:

The rule enumeration indicates the action that occurs when a ForeignKeyConstraint is enforced.None specifies that no action will occur, but exceptions are generated. This is what has occurred in this scenario.

 

Incorrect Answers:

 

A: Cascade specifies that all rows containing that value are also deleted.

B: SetNull specifies that values in all child columns are set to null values.

C: SetDefault specifies that all child columns be set to the default value for the column.

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Q:

You use Visual Studio .NET to develop a Windows-based application that interacts with a Microsoft SQL Server database. Your application contains a form named CustomerForm.

 You add the following design-time components to the form:

• SqlConnection object named XYZConnection.
• SqlDataAdapter object named XYZDataAdapter.
• DataSet object named XYZDataSet.
• Five TextBox controls to hold the values exposed by XYZDataSet.


At design time, you set the DataBindings properties of each TextBox control to the appropriate column in the DataTable object of XYZDataSet. When you test the application, you can successfully connect to the database. However, no data is displayed in any text boxes.

You need to modify your application code to ensure that data is displayed appropriately. Which behavior should occur while the CustomerForm.Load event handler is running?

A) Execute the BeginInit method of XYZDataSet. B) Execute the Open method of XYZConnection.
C) Execute the FillSchema method of XYZDataAdapter and pass in XYZDataSet. D) Execute the Fill method of XYZDataAdapter and pass in XYZDataSet.
 
Answer & Explanation Answer: D) Execute the Fill method of XYZDataAdapter and pass in XYZDataSet.

Explanation:

Dataset is a container; therefore, you need to fill it with data. You can populate a dataset by calling the Fill method of a data adapter.

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