Prevent ComboBox selection based on TextBox in Windows Application

Hi Ahmed.26,

Please share the combo box binding code and explain with an example.

So that we can make a sample for it.

Hello dharmendr,

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        GetRawTank1()
          GetRaw1()
End Sub
Private Sub GetRawTank1()
        ' CLEAR COMBOBOX 
        cbxrawtank1.Items.Clear()

        ' QUERY raw_tanks TABLE
        SQL.RunQuery("SELECT tank_name FROM raw_tanks where tank_name = 'Raw_Tank_A'")

        ' IF RECORDS ARE FOUND, ADD THEM TO THE COMBOBOX
        If SQL.RecordCount > 0 Then
            For Each r As DataRow In SQL.SQLDS.Tables(0).Rows
                cbxrawtank1.Items.Add(r("tank_name"))
            Next


        ElseIf SQL.Exception <> "" Then
            MsgBox(SQL.Exception)

        End If

    End Sub
Private Sub GetRaw1()
        ' CLEAR COMBOBOX 
        cbxraw1.Items.Clear()

        ' QUERY raw_materials TABLE
        SQL.RunQuery("SELECT material_name FROM raw_materials")

        ' IF RECORDS ARE FOUND, ADD THEM TO THE COMBOBOX
        If SQL.RecordCount > 0 Then
            For Each r As DataRow In SQL.SQLDS.Tables(0).Rows
                cbxraw1.Items.Add(r("material_name"))
            Next


        ElseIf SQL.Exception <> "" Then
            MsgBox(SQL.Exception)

        End If

    End Sub
Private Sub GetReading1(Tank1 As String)
        ' ADD SEARCH PARAMETER
        SQL.AddParam("@tank1", Tank1)


        ' RUN QUERY 
        SQL.RunQuery("SELECT reading from DATAGRID WHERE tank_name = '" & cbxrawtank1.Text & "' and material_name = @tank1")

        ' IF Tank IS FOUND, SEND Reading TO OUT TEXTBOX
        If SQL.RecordCount > 0 Then txt1.Text = SQL.SQLDS.Tables(0).Rows(0).Item("reading")

    End Sub
Private Sub cbxraw1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles cbxraw1.SelectedIndexChanged
        
        GetReading1(cbxraw1.Text)

    End Sub
Private Sub cmdupdate1_Click(sender As Object, e As EventArgs) Handles cmdupdate1.Click

        Dim UpdateCmd As String = "UPDATE DATAGRID " & _
                                   "SET reading +='" & txtupdate1.Text & "' " & _
                                   "WHERE tank_name ='" & cbxrawtank1.Text & "' AND material_name = '" & cbxraw1.Text & "'"
        

        If SQL.Update(UpdateCmd) = 0 Then

            MsgBox("The Specified raw_tank could not be found!")

        End If

        GetReading11(cbxraw1.Text)
        

    End Sub
Private Sub cmdfill1_Click(sender As Object, e As EventArgs) Handles cmdfill1.Click
        If txtupdate1.Text <> "" Or txt8.Text <> "" Or txt22.Text <> "" Or txt15.Text <> "" Then
            SQL.RunQuery("SELECT * FROM Report WHERE Report.tank_name = '" & cbxrawtank1.Text & "' and Report.material_name = '" & cbxraw1.Text & "' ")

            If SQL.SQLDS.Tables(0).Rows.Count > 0 Then
                MsgBox("Tank Already filled with another Material!")
                Exit Sub
            Else
                CreateUser()
                MsgBox("Instance is added to Report!")
            End If
        End If
        txtupdate1.Clear()
        txt8.Clear()
        txt15.Text = 0.0
        txt22.Text = 0.0
        GetReading1(cbxraw1.Text)
       

    End Sub
Private Sub cmdreset1_Click(sender As Object, e As EventArgs) Handles cmdreset1.Click
        Dim ResetCmd As String = "UPDATE DATAGRID " & _
                                   "SET reading ='" & 0.0 & "' " & _
                                   "WHERE tank_name ='" & cbxrawtank1.Text & "' AND material_name = '" & cbxraw1.Text & "'"
        If SQL.Update(ResetCmd) = 0 Then
            MsgBox("The Specified raw_tank could not be found!")
        End If
        GetReading1(cbxraw1.Text)
        

    End Sub
Private Sub cmdsub1_Click(sender As Object, e As EventArgs) Handles cmdsub1.Click

        Dim mynum1 As Integer = txt8.Text
        Dim mynum2 As Integer = txt1.Text
       
        If mynum1 <= mynum2 Then
            Dim subcmd As String = "UPDATE DATAGRID " & _
                        "SET reading -='" & mynum1 & "' " & _
                        "WHERE tank_name ='" & cbxrawtank1.Text & "' AND material_name = '" & cbxraw1.Text & "'"


            If SQL.Update(subcmd) = 0 Then

                MsgBox("The Specified tank could not be found!")

            End If
        Else
            MsgBox("You Can not Extract that amount!")
        End If
        GetReading12(cbxraw1.Text)


    End Sub
Public Sub CreateUser()
        Dim created_at As DateTime
        created_at = DateTime.Now.ToString("yyyy/MM/dd hh:mm:ss")

        ' ADD MEMBER TO DATABASE
        SQL.Addtank1(cbxrawtank1.Text, cbxraw1.Text, txt1.Text, txtupdate1.Text, txt15.Text, txt8.Text, txt22.Text, created_at)

    End Sub
Public Sub Addtank1(tank_name As String, material_name As String, before_add As String, added_value As String, after_add As String, exit_value As String, after_exit As String, created_at As DateTime)

        Try
            Dim strInsert As String = "INSERT INTO Report (tank_name,material_name,before_add,added_value,after_add,exit_value,after_exit,created_at) " & _
                                       "VALUES (" & _
                                       " ' " & tank_name & " '," & _
                                       " ' " & material_name & " '," & _
                                       " ' " & before_add & " '," & _
                                       " ' " & added_value & " '," & _
                                       " ' " & after_add & " '," & _
                                       " ' " & exit_value & " '," & _
                                       " ' " & after_exit & " '," & _
                                       " ' " & created_at & " ')"


            SQLCon.Open()
            SQLCmd = New SqlCommand(strInsert, SQLCon)

            SQLCmd.ExecuteNonQuery()
            SQLCon.Close()
        Catch ex As Exception
            MsgBox(ex.Message)

        End Try
    End Sub
 Private Sub cbxrawtank1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles cbxrawtank1.SelectedIndexChanged

        GetReading1(cbxraw1.Text)

        txt15.Text = 0.0
        txt22.Text = 0.0

    End Sub

Ahmed.26 says:

if the user tries to pick material_2 to fill the tank_1 while the tank_1 has an amount from material_1, a warning message pops up, says that "you must not add another material till the tank is empty!."

Please explain the above statement in more details.

If possible explain with proper example.

hello dharmendr, 

i have a text box "txt1.text" shows the reading of tank which it is in table called raw_tanks has two columns (tank_name,reading) , i created in sql.

in the beginning, when i choose tank from "cbxrawtank1" and choose material "cbxraw1" the reading "txt1.text" must be 0.0. 

when i begin to update the reading with adding value the txt1.text must be changed to the added value.

what i want to do and i have tried a lot actually, is when the reading becomes value more than 0.0 the material combo box "cbxraw1"  must freeze (if user attempts to select from material combo box again while reading is >0.0 ) so a warning messsage pops up says

"you are not allowed to add another material as tank is already filled"

Dear Ahmed.26,

You need to set ComoboBox Enable property False inside If Else condition and set lable value.

Please refere below sample.

Code

C#

public Form1()
{
    InitializeComponent();
    cbxraw1.Items.Add("Please selectt");
    cbxraw1.Items.Add("tank_name");
    cbxraw1.Items.Add("reading");

    cbxrawtank1.Items.Add("Please selectt");
    cbxrawtank1.Items.Add(" material");

    int num1 = 1;
    txtDetail.Text = num1.ToString();
    if(int.Parse(txtDetail.Text) > 0)
    {
        cbxraw1.Enabled = false;
        lblMsg.Text = "Error: you are not allowed to add another material as tank is already filled";
    }
}

VB.Net

Public Sub New()
    InitializeComponent()
    cbxraw1.Items.Add("Please selectt")
    cbxraw1.Items.Add("tank_name")
    cbxraw1.Items.Add("reading")
    cbxrawtank1.Items.Add("Please selectt")
    cbxrawtank1.Items.Add(" material")
    Dim num1 As Integer = 1
    txtDetail.Text = num1.ToString()

    If Integer.Parse(txtDetail.Text) > 0 Then
        cbxraw1.Enabled = False
        lblMsg.Text = "Error: you are not allowed to add another material as tank is already filled"
    End If
End Sub

Screenshot