ASP.NET- insert- delete-update

DataTables (disconnected datasets)

Shopping Basket

Insert

• Using the INSERT SQL statement with data hard-wired into it

• Using the INSERT SQL statement with placeholder variables to be filled by user input. – Parameters.Add used to fill placeholders

Insert using SQL commandOpen connection to database as usual, then:

Dim dothis As OleDbCommandDim strInsert As String

strInsert = "INSERT INTO Company (CompanyName, City) VALUES ('Blue Bird', 'Leeds')"

dothis= New OleDbCommand(strInsert, objConn)dothis.ExecuteNonQuery

Insert using Add method of OleDbCommandDim dothis As OleDbCommandDim strInsert As String

strInsert= "INSERT INTO Company (CompanyName, City) VALUES (@Company, @City)"

dothis= New OleDbCommand(strInsert, objConn)dothis.Parameters.Add("@Company",

txtCompany.Text)dothis.Parameters.Add("@City", txtCity.Text)

Dothis.ExecuteNonQuery

Delete

• SQL DELETE command

• SQL DELETE with Parameters.Add

Delete using SQLDim dothis As OleDbCommandDim strDelete As String

strDelete = “DELETE FROM” &;_ “Company WHERE CompanyName = ‘Blue Bird’”

dothis= New OleDbCommand(strDelete, objConn)

dothis.ExecuteNonQuery

Delete using Add method of OleDbCommand

strDelete = “DELETE FROM Company WHERE CompanyName = @CompanyName”

dothis= New OleDbCommand(strDelete, objConn)

dothis.Parameters.Add(“@CompanyName”, txtCompanyName.Text)

dothis.ExecuteNonQuery

Update

• Executing an SQL statement with the UPDATE command against the database.

• SQL UPDATE with Parameters.Add

Update using SQL

strUpdate = “UPDATE JobList SET EstimatedSalary = EstimatedSalary * 1.10 WHERE JobTitle = ‘Network Administrators’”

dothis= New OleDbCommand(strUpdate, objConn)

dothis.ExecuteNonQuery

Update using Add method of OleDbCommand

strUpdate = “Update JobList SET EstimatedSalary = @EstimatedSalary WHERE JobTitle = @JobTitle”

dothis= New OleDbCommand(strUpdate, objConn)dothis.Parameters.Add(“@EstimatedSalary”,txtEstimatedSalary.Text)dothis.Parameters.Add(“@JobTitle”, txtJobTitle.Text)dothis.ExecuteNonQuery

DataTables

• Table stored in server memory• Disconnected DataSet

• Used for– Manipulating subsets of data– Shopping basket

Defining a datatable1 – define columns

Dim objDT As System.Data.DataTable

objDT = New System.Data.DataTable("Cart")

objDT.Columns.Add("Product", GetType(String))objDT.Columns.Add("Quantity", GetType(Integer))objDT.Columns.Add("Cost", GetType(Decimal))

Data Table - Header Row

Product Quantity Cost

After step 1

Step 2 Adding a new row

Dim objDR As System.Data.DataRow

objDR = objDT.NewRow

Part A – create a new blank row that copies the table

After Step 2a

Data Table (objDT)- Header Row

Product Quantity Cost

DataRow (objDR)

2b – fill the new row

objDR("Quantity") = txtQuantity.Text

objDR("Product") = ddlProducts.SelectedItem.Text objDR("Cost") = Decimal.Parse(ddlProducts.SelectedItem.Value)

After step 2b

Data Table (objDT)- Header Row

Product Quantity Cost

DataRow (objDR)

Something some number some price

Step 3 – put the new row in the table

objDT.Rows.Add(objDR)

After step 3

Data Table (objDT)

Product Quantity Cost

Something some number some price

Header Row

Row 1

Shopping Basket

• User not logged in*– Session– Datatable stored in memory

• User logged in– Session– Datatable to & from database

* This version for coursework

Shopping Basket

Initialise basket

1. Create a datatable2. Store it in memory (Session)

Session(“cart”)=objDT

Shopping basket (cont 2)

When “add to cart” clicked1. Retrieve the datatable from memory2. Create a new row3. Fill in the data4. Put the new row on the bottom of the

datatable

basket = Session(“cart”)

Shopping basket (cont 3)

View Basket

1.Retrieve table from memory2.Bind table to DataGrid

BasketGrid.DataSource()=Session(“cart”)

TO DO• Oasisplus

– ASP.NET : INSERT, DELETE, UPDATE– ASP.NET : DataList– Shopping basket example code on discussion

board

– Or start your coursework

• NEXT WEEK– SHOPPING BASKET

• Where we take items from a list retrieved from the database