Tài liệu Put the Finishing touches On A Data Bound Form pdf

In this case, you will see how to do the following: • Toggle the enabled property of the btnSave, btnCancel, btnNew, and btnDelete at the appropriate moments, such as when a record is

1.7 Put the Finishing Touches on a Data Bound Form

Besides handling the basics, you need to add some finishing touches to a data entry form, such as enabling/disabling controls based on whether you're on a record This How-To shows you how to use the Enabled properties on controls to give the user more direction when using a Windows form (see Figure 1.12)

Figure 1.12 You will create this complete form by How-To 1.7, with all the bells and

whistles that users expect from a good data entry form

Although the majority of the major issues are taken care of for the form you created so far in the chapter, your users become confused about when to push some of the buttons How do you get the buttons to reflect when the users can click them, and what other finishing touches might help the form?

Technique

An important part of user interfaces is letting the user know when he has access to certain features on the form In this case, you will see how to do the following:

• Toggle the enabled property of the btnSave, btnCancel, btnNew, and btnDelete at

the appropriate moments, such as when a record is highlighted in the list box

• Add a command button to close the form

• Add code to the Closing event of the form that tests whether you have made

changes to the current record, and if so, whether you want to save the changes You can see an example of particular command buttons being enabled based on the

current action being performed in the form in Figure 1.13

Figure 1.13 This form allows users to access command buttons only when the

functionality is available

Steps

Continuing on with the form that you have been using, you are going to make the

changes just mentioned in the previous bulleted list

1 Start by modifying two routines already created: RefreshIndividual and

ActivateEditing subroutines Then check whether a customer has been selected in lstCustomers If not, then the two buttons, btnEdit and btnDelete, are disabled If a customer hasn't been selected, the two buttons are enabled, and the

dsCustomerIndividual dataset control is refreshed

Listing 1.19 frmHowTo1_7.vb: Toggling the Enabled Property of the btnEdit and btnDelete Buttons

Private Sub RefreshIndividual()

'- Clear individual customer dataset

Me.dsCustomerIndividual.Clear()

If lstCustomers.SelectedIndex = -1 Then

btnEdit.Enabled = False

btnDelete.Enabled = False

Else

btnEdit.Enabled = True

btnDelete.Enabled = True

Me.odaCustomerIndividual.SelectCommand.Parameters(0).Value =

lstCustomers.SelectedItem(0)

'- Fill the dataset

Me.odaCustomerIndividual.Fill(Me.dsCustomerIndividual, "Customers")

End If

End Sub

Similarly, you will add code to the ActivateEditing subroutine to toggle the Enable property of the various command buttons, depending on their purpose Listing 1.20 shows the entire routine

Listing 1.20 frmHowTo1_7.vb: Toggling the Enabled Property of btnEdit and btnDelete Buttons

Private Sub ActivateEditing(ByVal bEnable As Boolean)

Dim oCurr As Object

'- Loop through each of the controls on the form

For Each oCurr In Me.Controls()

'- Check to see if the control is a text box

If TypeOf oCurr Is TextBox And oCurr.Name <> "txtCustLimit" Then

'- If so, toggle the properties

If bEnable Then

oCurr.BorderStyle() = _

System.Windows.Forms.BorderStyle.Fixed3D

oCurr.BackColor() = System.Drawing.Color.White

Else

oCurr.BorderStyle() = _

System.Windows.Forms.BorderStyle.FixedSingle

oCurr.BackColor() = Me.BackColor

End If

oCurr.Enabled = bEnable

End If

Next

'- Enable/Disable the appropriate buttons

btnEdit.Enabled = Not bEnable

btnNew.Enabled = Not bEnable

btnDelete.Enabled = Not bEnable

btnCancel.Enabled = bEnable

btnSave.Enabled = bEnable

'- Set the focus to the CustomerID text box

If bEnable Then

Me.txtCustomerID.Focus()

End If

End Sub

The specific lines of code added are shown here:

'- Enable/Disable the appropriate buttons

btnEdit.Enabled = Not bEnable

btnNew.Enabled = Not bEnable

btnDelete.Enabled = Not bEnable

btnCancel.Enabled = bEnable

btnSave.Enabled = bEnable

These buttons are handled as the other buttons are-by taking the opposite value to which bEnable is currently set, and using it to toggle the Enabled property

Finally, if the bEnable flag is True, then focus is moved to the txtCustomerID text box using the following lines of code:

'- Set the focus to the CustomerID text box

If bEnable Then

Me.txtCustomerID.Focus()

End If

End Sub

2 Add a new command button, with the properties Name and Text set to btnClose and &Close, respectively Place the code in Listing 1.21 for the Click event

Listing 1.21 frmHowTo1_7.vb: Close the Form

Private Sub btnClose_Click(ByVal sender As System.Object, _

ByVal e As System.EventArgs) Handles btnClose.Click

Me.Close()

End Sub

3 Add some code to the Closing event of the form Listing 1.22 tests whether the btnSave button is enabled If it is, the MessageBox method is evoked, asking the user if he wants to save changes that were made If so, then the SaveRecord is called within a Try Catch End Try block

Listing 1.22 frmHowTo1_7.vb: Checking Whether the User Wants to Save a Record Before Closing

Private Sub frmHowTo1_7_Closing(ByVal sender As Object, _

ByVal e As System.ComponentModel.CancelEventArgs) Handles

MyBase.Closing

'- If an edit or add has been requested, enabling the Save button,

' then prompt to save the record

If btnSave.Enabled Then

If MessageBox.Show("Would you like to save the current record?", _ "Save Record?", MessageBoxButtons.YesNo) = _

DialogResult.Yes Then

Try

'- Save the information

SaveRecord()

Catch saveException As Exception

If MessageBox.Show("The following error has occurred: " &

saveException.Message & vbCrLf & vbCrLf & _

"Continue with closing the form?", "Error Saving Record",

MessageBoxButtons.YesNo) = DialogResult.No Then

e.Cancel = True

End If

End Try

End If

End If

End Sub

How It Works

In the modifications made to the form in this How-To, many things happen depending on what is occurring When the user clicks the btnEdit button, btnEdit, btnNew, and

btnDelete are disabled, and btnCancel and btnSave are enabled The opposite is true when btnCancel and btnSave are pressed If bEnable is True, then the focus is moved to the txtCustomerID text box

When the txtClosed button is clicked, the application then checks whether the btnSave command button has been enabled, meaning data is being edited If so, then the user is asked whether he wants to save the current record If the user does, the system then saves the current information back to the server

Comments

The tasks displayed in this How-To are just a few of the tasks you can do to make your forms look and feel more professional They are also what users come to expect from database applications

Play with the form a bit more You're sure to come up with a few more ideas