Information Systems Engineering

Transcription

1 Connection to a DB Information Systems Engineering Data from Databases Using ASP.NET Several ASP.NET controls allow the presentation of data from a datasource The datasource can be a database The association between a presentation control and a datasource is called a databind When the datasource is a database we need a special control to do the connection to the DBMS This control needs to know what is the DBMS What is the database What query to use to retrieve the data The returned table is then passed to the presentation control It is also possible to do the reverse way From the presentation to the database we do insertions, updates and deletions 1 MIB - ESIN apm@feup 2 DB connection and databind The SqlDataSource control DBMS update select DataSource control Database connection SQL commands (select, insert, update, delete) Represents the connection to a SQL Server Retrieves the results of a SELECT query Can perform an INSERT, DELETE and UPDATE statements Can be linked (databound) to a variety of display controls databind Server name: <machine>\sqlexpress Visualization Access credentials Database name MIB - ESIN apm@feup 3 MIB - ESIN apm@feup 4

2 The SqlDataSource configuration SQL commands in SqlDataSource For a written specification of the Select, Insert, Update and Delete commands If we need only a simple Select query we can specify it visually Specifying the Select query The Query Builder can help in the specification MIB - ESIN apm@feup 5 MIB - ESIN apm@feup 6 Finishing the specification The last step allows us to test the Select command correctness Linking a data source to a control Data source controls can be bound to list presenting controls e.g. ListBox, DropDownList, BulletedList, RadioButtonList and CheckBoxList You need only to indicate the data source control name in the property DataSourceID 2 columns of the data source (can be the same) The DataTextField property holds the names that are shown in the page The DataValueField property can hold associated values retrievable on a post-back (e.g. associated to the selected item) Visual Studio has a simple tool to specify the data source binding to a List control MIB - ESIN apm@feup 7 MIB - ESIN apm@feup 8

3 Linking to a list control Databound list controls The column, from the select command result, that will supply the items to be displayed by the list control The column, from the select command result, that will supply the values associated to the displayed items in the list control MIB - ESIN apm@feup 9 MIB - ESIN apm@feup 10 SQL command parameters SQL command parameters When we specify the SQL commands in a data source we can use parameters Parameters have names started Example: SELECT (fname + ' ' + lname) AS [Member Name] FROM Member WHERE is a parameter The parameters can be associated to other controls properties When we define a command with parameters Visual Studio asks for that association A parameter can has as properties the controlid and PropertyName Has also a default value (used if the control is empty) Can has also a DbType or a Type Main parameter properties Parameter MIB - ESIN apm@feup 11 MIB - ESIN apm@feup 12

4 Parameter advanced properties Testing the query with parameters MIB - ESIN apm@feup 13 MIB - ESIN apm@feup 14 Table visualization - GridView The GridView control is drawn as a table and shows several columns of a data source It shows the result of a SELECT command from a data source The data source is bound in the DataSourceID property The columns can be reordered and we can choose the ones to be shown We can allow the user to sort the table rows by any column, clicking the header If the number of rows is big, we can display them in separate pages There are many appearance properties allowing the programmer to change the view style in innumerous ways GridView configuration Column properties configuration MIB - ESIN apm@feup 15 MIB - ESIN apm@feup 16

5 DetailsView control DataList Control MIB - ESIN apm@feup 17 MIB - ESIN apm@feup 18