PROG11044 - Advanced Web Apps 4/13/2019 Programming Data Pages Wendi Jollymore, ACES

Review So Far Classes we used: SqlConnection SqlCommand A connection object that facilitates communication with the database SqlCommand A command object that models a specific SQL command to be executed over a specific connection Connection property – references a connection object CommandText property – contains the SQL command to execute 4/13/2019 Wendi Jollymore, ACES

Review So Far SqlDataReader A forward-only, read-only set of records Returned by the command object’s ExecuteReader() method command.ExecuteReader() executes the CommandText query over the Connection object The resulting rows or records are returned as a Data Reader object 4/13/2019 Wendi Jollymore, ACES

Review So Far SqlDataReader, continued Read() method Returns true if it read a record Used to move through the records reader[“fieldName”] syntax Allows you to access the field values in the current record 4/13/2019 Wendi Jollymore, ACES

Review So Far SqlParameter Some SQL statements will contain values that are dynamic E.g. select * from authors where authorID = ? The ? Value could come from a list box selection Parameter objects are used to replace unknown or variable values More secure than concatenating values together to build SQL statements 4/13/2019 Wendi Jollymore, ACES

The DataSet Object System.Data.DataSet A virtual database The client machine can download a copy of the tables/query results they want DataSet data can be modified You can move around in a data set i.e. it’s not forward-only The data set object can be used with any provider 4/13/2019 Wendi Jollymore, ACES

The DataSet Object A DataSet contains a collection of tables It contains information about the tables, such as: Schema Records Relationships Constraints 4/13/2019 Wendi Jollymore, ACES

The DataSet Object DataSet.Tables property References the collection of tables This collection object is an instance of the DataTableCollection class A DataTableCollection object contains a set of DataTable objects Each DataTable object in the DataTableCollection is one of the tables in the database 4/13/2019 Wendi Jollymore, ACES

The DataSet Object Ways to reference a table in the dataset: dataSet.Tables[“Books”] dataSet.Tables[0] 4/13/2019 Wendi Jollymore, ACES

The DataTable Object Models a table from the database dataTable.Rows property References the DataRowCollection object A collection of DataRow objects The set of rows (records) in the table 4/13/2019 Wendi Jollymore, ACES

The DataTable Object dataTable.TableName property The name you gave the table when you added it to the data set dataTable.Columns property References the DataColumnCollection object A collection of DataColumn object The set of columns (fields) in the table dataTable.Columns.Count property The number of columns in the table 4/13/2019 Wendi Jollymore, ACES

The DataRow Object Models a row (record) in the row collection of the table dataTable.Rows.Count property The number of DataRow objects in the DataRowCollection i.e. the number of records dataTable.Rows.Find(keyValue) Used to locate a specific record in the collection keyValue is the value for the primary key field to match 4/13/2019 Wendi Jollymore, ACES

The SqlDataAdapter Object A data adapter facillitates communication between the DataSet and the data source DataSet is not provider specific Everything else is The data adapter will pass any data from the data source to the DataSet The data adapter will also handle the data manipulation for you 4/13/2019 Wendi Jollymore, ACES

The SqlDataAdapter Object SelectCommand property Contains a command object that contains a SELECT query UpdateCommand, DeleteCommand, InsertCommand properties Contains command objects for UPDATE, DELETE, and INSERT commands Command objects have their own connection, so that connection is used to execute the various commands 4/13/2019 Wendi Jollymore, ACES

The SqlDataAdapter Object dataAdapter.Fill(dataSet) method Executes the query in the SelectCommand property’s command object Fills the dataset with the results of that query dataAdapter.Fill(dataSet, strName) As above but assigns the result table with strName as a table name Accessed via dataSet.Tables[strName] 4/13/2019 Wendi Jollymore, ACES

Exercise ADO Notes: “Advanced Programming” Do the tutorial “Working with the DataSet” Do the “Multiple Tables in a DataSet” tutorial and exercise 4/13/2019 Wendi Jollymore, ACES

Iterating Through Records There are a few ways you can iterate through the collection of data rows (records) The rows collection can be used to access records and field values: Get the third row: DataRow aRow = dataSet.Tables[“Authors”].Rows[3]; Get the last name field value from the 1st row: String lastName = aRow[“lastName”]; String lastName = dataSet.Tables[“Authors”].Rows[3][“lastName”]; 4/13/2019 Wendi Jollymore, ACES

Iterating Through Records dataRow.ItemArray property References the field values in a row as an array of generic objects You can retrieve this array and then iterate through it: object[] values = dataSet.Tables[“Books"].Rows[rowIndex].ItemArray; for (int i=0; i<values.Length; i++) { string output += values[i].ToString(); } 4/13/2019 Wendi Jollymore, ACES

Exercise Try the two exercises in the section “Displaying Records Programmatically” Do the “Navigating Records” exercise 4/13/2019 Wendi Jollymore, ACES