In preceding lessons, you have learned how to connect to a database as well as filling up the table with data in Visual Basic 2022, now you shall learn how to manipulate the data in the database. Manipulating data means adding news records, editing records, deleting records, browsing records and more.
In this lesson, we will create command buttons and write relevant codes to allow the user to browse the records forward and backward as well as fast forward to the last record and back to the first record. The first button we need to create is for the user to browse the first record. We can use button’s text << to indicate to the user that it is the button to move to the first record and button’s text >> to move to the last record. Besides we can use button’s text < for moving to previous record and button’s text > for moving to the next record.
The code for moving to the first record is:
MyRowPosition = 0 Me.showRecords()
The code for moving to previous record is:
If MyRowPosition > 0 Then MyRowPosition = MyRowPosition – 1 Me.showRecords() End If
The code for moving to next record is:
If MyRowPosition < (MyDataTbl.Rows.Count – 1) Then MyRowPosition = MyRowPosition + 1 Me.showRecords() End If
The code for moving to last record is:
If MyDataTbl.Rows.Count > 0 Then MyRowPosition = MyDataTbl.Rows.Count – 1 Me.showRecords() End If
You can edit any record by navigating to the record and change the data values. However, you need to save the data after editing them. You need to use the update method of the SqlDataAdapter to save the data. The code is:
If MyDataTbl.Rows.Count <> 0 Then MyDataTbl.Rows(MyRowPosition)(“ContactName”) = txtName.Text MyDataTbl.Rows(MyRowPosition)(“state”) = txtState.Text MyDatAdp.Update(MyDataTbl) End If
You can also add new record or new row to the table using the following code :
Dim MyNewRow As DataRow = MyDataTbl.NewRow() MyDataTbl.Rows.Add(MyNewRow) MyRowPosition = MyDataTbl.Rows.Count – 1 Me.showRecords()
The code above will present a new record with blank fields for the user to enter the new data. After entering the data, he or she can then click the Save button to save the data.
Lastly, the user might want to delete the data. The code to delete the data is:
If MyDataTbl.Rows.Count <> 0 Then MyDataTbl.Rows(MyRowPosition).Delete() MyDatAdp.Update(MyDataTbl) MyRowPosition = 0 Me.showRecords() End If
Public Class Form1 Private MyDatAdp As New SqlDataAdapter Private MyCmdBld As New SqlCommandBuilder Private MyDataTbl As New DataTable Private MyCn As New SqlConnection Private MyRowPosition As Integer = 0 Private Sub Form1_FormClosed(sender As Object, e As FormClosedEventArgs) Handles Me.FormClosed MyCn.Close() MyCn.Dispose() End Sub Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load MyCn.ConnectionString = "Data Source=TOSHIBA-PC\SQL2012; AttachDbFilename=C:\Program Files\Microsoft SQL Server\MSSQL11.SQL2012\MSSQL\DATA\Test.mdf; " & _ "User Instance=True;Integrated Security=SSPI" MyCn.Open() MyDatAdp = New SqlDataAdapter("Select* from Contacts", MyCn) MyCmdBld = New SqlCommandBuilder(MyDatAdp) MyDatAdp.Fill(MyDataTbl) Dim MyDataRow As DataRow = MyDataTbl.Rows(0) Dim strName As String Dim strState As String strName = MyDataRow("ContactName") strState = MyDataRow("State") TxtName.Text = strName.ToString TxtState.Text = strState.ToString Me.showRecords() End Sub Private Sub showRecords() If MyDataTbl.Rows.Count = 0 Then txtName.Text = "" txtState.Text = "" Exit Sub End If txtName.Text = MyDataTbl.Rows(MyRowPosition)("ContactName").ToString TxtState.Text = MyDataTbl.Rows(MyRowPosition)("State").ToString End Sub Private Sub BtnMoveFirst_Click(sender As Object, e As EventArgs) Handles BtnMoveFirst.Click MyRowPosition = 0 Me.showRecords() End Sub Private Sub BtnMovePrev_Click(sender As Object, e As EventArgs) Handles BtnMovePrev.Click If MyRowPosition > 0 Then MyRowPosition = MyRowPosition - 1 Me.showRecords() End If End Sub Private Sub BtnMoveNext_Click(sender As Object, e As EventArgs) Handles BtnMoveNext.Click If MyRowPosition < (MyDataTbl.Rows.Count - 1) Then MyRowPosition = MyRowPosition + 1 Me.showRecords() End If End Sub Private Sub BtnMoveLast_Click(sender As Object, e As EventArgs) Handles BtnMoveLast.Click If MyDataTbl.Rows.Count > 0 Then MyRowPosition = MyDataTbl.Rows.Count - 1 Me.showRecords() End If End Sub Private Sub BtnAdd_Click(sender As Object, e As EventArgs) Handles BtnAdd.Click Dim MyNewRow As DataRow = MyDataTbl.NewRow() MyDataTbl.Rows.Add(MyNewRow) MyRowPosition = MyDataTbl.Rows.Count - 1 Me.showRecords() End Sub Private Sub BtnDelete_Click(ByVal sender As Object, ByVal e As EventArgs) Handles BtnDelete.Click If MyDataTbl.Rows.Count <> 0 Then MyDataTbl.Rows(MyRowPosition).Delete() MyRowPosition = 0 MyDatAdp.Update(MyDataTbl) Me.showRecords() End If End Sub Private Sub BtnSave_Click(ByVal sender As Object, ByVal e As EventArgs) Handles BtnSave.Click If MyDataTbl.Rows.Count <> 0 Then MyDataTbl.Rows(MyRowPosition)("ContactName") = TxtName.Text MyDataTbl.Rows(MyRowPosition)("state") = TxtState.Text MyDatAdp.Update(MyDataTbl) End If End Sub End Class
The Visual Basic 2022 database program UI is as shown in Figure 36.1.
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