The myReader. Read method returns a boolean value, which indicates whether there are more records to be read. The results of the SQL query are displayed in a message box.
The end of the procedure should appear as follows:. For more information about using ADO. NET Help documentation. Skip to main content. This browser is no longer supported. Download Microsoft Edge More info. Contents Exit focus mode. Please rate your experience Yes No. Click Sign In to add the tip, solution, correction or comment that will help other users. Report inappropriate content using these instructions. NET: Best practices Part 1. MS-Access with VB. Imports System.
Public Class Form1. EmployeeID, Employees. LastName, Employees. Title, Employees. Dim ds As New DataSet. Add employeeTable. Load cmd. ExecuteReader , LoadOption. OverwriteChanges, employeeTable. Tables "Employees". Columns "EmployeeID". Catch ex As Exception. End Try. End Using. End Sub. FirstName, Employees. BirthDate, Employees. MsgBox ex. TitleOfCourtesy, Employees. AddWithValue "?
Show ds. Tables 0. End Class. Public Interface IConnection. End Interface. Another advantage for ensuring both have a ConnectionString property is when a move is made from MS-Access to SQL-Server in regards to connections only the actual data provider changes. AccessConnection also has a connection string for encrypted database password while SQL-Server does not, instead SQL-Server security is usually handled by active directory in tangent with properly setting up security in the database.
Considerations for login process. A login should at the very least provide an interface to permit user name and password to be entered and allow multiple login attempts. Basic login projects. Front end.
Back end. Additional options, reveal password, provide a method to reset their password or contact someone who can reset the password. Encryption of a database. Open the selected database in exclusive mode. Under the File menu select "Encrypt with Password" Enter the password. Close the database and test with a connection string with the password. Under File, options, client settings. Scroll to the bottom Change default encryption to "use legacy encryption" Press OK Re-test, if there is an issue there is another known thing to try, shorten the password to under 14 in length.
Implementing secure connections Using ConfigurationLibrary in the supplied source, add this project to a Visual Studio solution followed by adding a new reference in your project to ConfigurationLibrary.
Using the connection string created above, under project properties, settings. Create a new setting of type Connection String with a name of your choice. Create a private variable of type ConnectionProtection as in first code block below Encrypt see second code block below in your form or data class before using a connection and before deploying out in production. Access the encrypted connection string see third code block below followed by opening a connection.
If Not operations. IsProtected Then. End If. Return True. Return IsSuccessFul. End Function. Inherits BaseExceptionProperties. Implements IConnection.
BaseExceptionProperties : by inheriting this class all exception handling will have a common method to capture exception information along with providing a way to determine if a method was successful or unsuccessful. In the following code block a DataTable is returned even if there is an exception thrown. FROM Customer. Return dt. If ops. IsSuccessFul Then. When designing a database, there is a temptation to place related data into one table which in short will cause issues down the road.
A good example, a customer table which has a contact first name, last name and title. In the case title should reside in a reference table with a foreign key back to the customer table. Each record in the customer table now needs to be updated while using a reference table, make the change in the reference table and all records with Assistant Manager are now Assistant Sales Manager. Secondly, the database needs to be in a trusted location on your computer, or on whatever computer it resides on.
If this is not the case, an attempt to add or update records may cause problems, as you will need write permission for the target directory. The variable con now holds a reference to the connection object. The ConnectionString property of the connection object should specify both the technology to be used to connect to the database the database provider , and the location of the database file the data source.
If the database were password protected, it would also need to include a valid username and password. This code creates a connection object and a connection string. To open the database, we use the Open method of the connection object. After we have finished working with the database, it should be closed using the Close method.
Open MsgBox "A connection to the database is now open. Close MsgBox "The connection to the database is now closed. Your coding window should now look like the illustration below. You can run the program now to check that it can open and close the database. Once the program is running, click on the button you created; you should see a message that tells you that the connection to the database is open.
Close this message box, and you should see another message box telling you that the connection is closed if you get an error message, make sure that your database is in the location you specified. The application can now open and close the database connection. Net uses an object called a DataSet to hold information read from the database alternatively, an object called a DataTable is available if you just want to read information, as opposed to writing new or modified information to the database.
Another object, called a Data Adapter , is used to communicate between the connection object and the dataset. We will need to create additional variables to hold references to the data adapter and dataset objects.
We will also need to create string variables to hold the commands we will be sending to the database. OleDbDataAdapter sql, con. The application now has a data adapter, a dataset and an SQL command. The data adapter can fill a dataset with records from a table using its Fill method, which takes two parameters. The first parameter will be the name of the variable that holds the reference to the dataset object in this case ds.
The second is a name that will be used to identify this particular data adapter fill, and can be anything you like but it should be meaningful. This code fills the dataset ds with data from the Contact table in the database. The only problem is that the data itself cannot be seen by the user.
The next thing we need to do, therefore, is to display the data in an appropriate format. To do this:. Tables "Contacts". Rows 0. Item 1. ToString txtLastName. Item 2. The first line of code assigns the contents of row 0 , column 1 of the table to the Text property of txtFirstName. The second line of code assigns the contents of row 0 , column 2 of the table to the Text property of txtLastName.
The ToString function is called here because any field that does not contain data will return a Null value, which cannot be displayed in a text box - the function replaces the Null value with an empty string "". Remember that rows and columns are indexed from zero, and that the first column in the table is the ContactID field, which we are not currently interested in. Row 0 thus points at the first record in the table, column 1 is the FirstName field, and column 2 is the LastName field you could also use the field name to reference the required column, rather than the column number.
If you run the program and click on the button just click on OK when the connection status messages are displayed, to get rid of the message boxes , you should see the name "Chris Wells" displayed in the two text boxes. The application can now display some data from a database table. In order to see a different record, we need to use a different row number. In fact, we can scroll through the entire table by incrementing the row number to view each record in turn.
Proceed as follows:. Dim con As New OleDb. OleDbDataAdapter sql, con da. Fill ds, "Contacts" con. The two integer variables maxRows and inc are used to store the total number of records in the data set using the Count method of the Rows property , and to keep track of the current record number when navigating backwards and forwards through table using the variable inc , which is initialised to 0.
Rows inc. ToString End Sub.
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