从SQL显示数据到vb.net文本框

Question

I'm trying to retrieve data from sql server to vb.net textbox but i don't know what else to do all the tutorials i have are just to retrieve records from the database to datagrid view..please help..

Private Sub txtrfid_KeyPress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles txtrfid.KeyPress
    cn.Open()

    With cmd
        .Connection = cn
        .CommandText = "SELECT * FROM Students WHERE RFID like '%" & txtrfid.Text & "%'"
    End With
    MsgBox("Record Found!", MsgBoxStyle.Information, "Update")

    da.SelectCommand = cmd
    dt.Clear()
    da.Fill(dt)
    cn.Close()


    txtname.Text = 'Firstname'

Answer 1

You're populating a DataTable with the data from the database so you then have to get the data from that DataTable into the TextBox . You can do that with data binding, which is how you've probably seen it done with a grid, eg

txtname.DataBindings.Add("Text", dt, "Firstname")

That's definitely how you'd do it if you were retrieving multiple records that you wanted to be able to navigate, although you'd probably use a BindingSource in between. If there's only one record then you might instead just move the data manually, eg

txtname.Text = CStr(dt.Rows(0)("Firstname"))

Answer 2

If you want to display only a single value ( FirstName ) from Table then see following piece of code

Using conn As New SqlConnection("connstr")
      conn.Open()
      Dim cmd As New SqlCommand("", conn)
      Dim txtName As String
      cmd.CommandText = "SELECT firstname FROM Students WHERE RFID ='" & txtrfid.Text & "'"
      txtName = IIf(IsDBNull(cmd.ExecuteScalar), "", cmd.ExecuteScalar)
      If txtName <> "" Then
         MsgBox("Record Found!", MsgBoxStyle.Information, "Update")
         Textbox1.Text = ""
         Textbox1.Text = txtName
      else
         MsgBox("No Record Found!", MsgBoxStyle.Information, "INFO.")
      End If
 End Using

Answer 3

There are many ways to retrieve the data. You can simply retrieve the data from sql database to textbox using sql data reader which is one of my favourite. Let me share to you. Note : Don't forget to import system.data.sqlclient

Private Sub txtrfid_KeyPress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles txtrfid.KeyPress
        strConn = "Data Source=" & servernamehere & ";Initial Catalog=" & databasenamehere & ";User ID=" & userid & ";Password=" & password
        sqlConn = New SqlConnection(strConn)
        sqlConn.Open()
        Dim sqlcmd As New SqlCommand("Your query here", sqlConn)
        Dim myreader As SqlDataReader
        myreader = sqlcmd.ExecuteReader()
        myreader.Read()
        If myreader.HasRows Then
            txtrfid.Text = myreader.Item("column name from sql database table").Tostring
        End If
        sqlConn.Close()
End Sub

You may catch the exception with Try-Catch Technique.