Add new data to textbox when selecting item from combobox - asp.net

Question

How can I automatically input a number to a textbox after clicking a button upon selecting an item from a combobox. All I know to do is to get the data from the combobox to textbox. But what I would like to do is to add data to a textbox once the item is selected.
This is My Code:
Imports System.Data.OleDb
Imports System.Data
Public Class voting1
Dim con As New OleDbConnection
Dim Com As New OleDbCommand
Dim ComInsert As New OleDbCommand
Dim ComUpdate As New OleDbCommand
Dim ComDelete As New OleDbCommand
Dim aAdapter As New OleDbDataAdapter
Dim Dset As New DataSet
Private Sub voting1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim ConProvider As String = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=J:\EvS\EVS.accdb"
Try
Try
con.ConnectionString = ConProvider
If Not con.State = ConnectionState.Open Then
con.Open()
End If
Catch ex As Exception
MsgBox("No Connection Established")
End Try
Me.fill()
user.Visible = False
user.Text = Form1.usertxt.Text
Catch ex As Exception
End Try
End Sub
Private Sub fill()
With aAdapter
.SelectCommand = New OleDb.OleDbCommand()
.SelectCommand.CommandText = "select * from candidate"
.SelectCommand.Connection = con
End With
Dim dataRead As OleDb.OleDbDataReader
dataRead = aAdapter.SelectCommand.ExecuteReader()
While (dataRead.Read())
presbox.Items.Add(dataRead("President"))
vpbox.Items.Add(dataRead("VicePresident"))
secbox.Items.Add(dataRead("Secretary"))
treasbox.Items.Add(dataRead("Treasurer"))
End While
aAdapter.Dispose()
End Sub
Public Sub Initialize()
Try
If Not con.State = ConnectionState.Open Then
con.Open()
End If
Catch ex As System.Exception
MsgBox(ex.Message, MsgBoxStyle.Information, "ERROR CONNECTION")
End Try
End Sub
Private Sub bo()
Dim con1 As New OleDbConnection
Dim cmd As New OleDbCommand
con1.ConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=J:\EvS\EVS.accdb"
cmd.Connection = con1
con1.Open()
Dim num As Integer
cmd.CommandText = "SELECT pres1 FROM vote1"
If IsDBNull(cmd.ExecuteScalar) Then
num = 1
samp.Text = num
Else
num = 1
samp.Text = num
End If
cmd.Dispose()
con1.Close()
con1.Dispose()
End Sub
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Try
Call Initialize()
If presbox.Text = "" Or vpbox.Text = "" Or secbox.Text = "" Or treasbox.Text = "" Then
MsgBox("All Fields are required, Check the fields", MsgBoxStyle.Information, "Required Fiels")
Exit Sub
End If
With aAdapter
.SelectCommand = New OleDb.OleDbCommand()
.SelectCommand.CommandText = "select * from [vote] where username = '" & user.Text & "'"
.SelectCommand.Connection = con
End With
Dim dataRead As OleDb.OleDbDataReader
dataRead = aAdapter.SelectCommand.ExecuteReader()
If Not dataRead.HasRows Then
ComInsert.CommandText = "INSERT INTO vote([username],[president],[vicePresident],[secretary],[treasurer])" & _
"VALUES('" & user.Text & "','" & presbox.Text & "','" & vpbox.Text & "','" & secbox.Text & "','" & treasbox.Text & "')"
ComInsert.Connection = con
ComInsert.ExecuteNonQuery()
MsgBox("Voting Successful!", MsgBoxStyle.Information, "NEW RECORD")
Form1.Show()
Me.Close()
aAdapter.Dispose()
ComInsert.Dispose()
Else
MsgBox("WARNING: User Voted Already!!", MsgBoxStyle.Exclamation, "ERROR SAVING DATA")
Me.Close()
Form1.Show()
End If
Catch ex As Exception
End Try
End Sub
End Class

Answer 1

There are a couple of ways to do this if I am understanding what you are wanting.
1.) We can just check if there is anything in the combobox.text property.
If String.IsNullOrEmpty(cbobox.text) Then
Perform the logic of adding data to textbox here.
cbobox.text = null
End If
That is the most simple way, but you will have to set the combobox back to null after the data is added to make it work again.
2.) We can make use of the Combobox.SelectedIndexChanged method.
Here is the documentation website: http://msdn.microsoft.com/en-us/library/system.windows.forms.combobox.selectedindexchanged.aspx
Here is an example:
private void ComboBox1_SelectedIndexChanged(object sender,
System.EventArgs e)
{
perform logic here
}
Hope this helps.

Answer 2

Private Sub p1()
If Not con.State = ConnectionState.Open Then
con.Open()
End If
Com = con.CreateCommand
Com.CommandText = "SELECT COUNT(vote.presnum) as countofpres FROM vote WHERE presnum ='1';"
Dim dt As OleDb.OleDbDataReader = Com.ExecuteReader
dt.Read()
Dim countpres As Integer = dt("countofpres")
Me.pres1.Text = countpres
dt.Close()
End Sub
here it is Jlott