CODEWITHSUNDEEP
c#variablesserial-portglobal-variables
user1913707
user1913707

Reputation: 43

How to declare a c# variable for a picked item from a combobox

How do I create a public variable for a selected value in my comboBox1 so that it can be used in every button so I don't have to repeat it for every button? For every button I have:

var portNum = comboBox1.SelectedItem.ToString();
using (SerialPort port = new SerialPort( portNum, 9600, Parity.None, 8))

But I want to just have portNum and not have to put the var declaration line in every button.

public partial class planar232 : Form
{
    private SerialPort comPort = new SerialPort();
    private string[] ports = SerialPort.GetPortNames();


    public planar232()
    {
        InitializeComponent();
        foreach (string port in ports)
        {
            comboBox1.Items.Add(port);
        }

    }

    private void Form1_Load(object sender, EventArgs e)
    {

    }

    private void button1_Click(object sender, EventArgs e)
    {
        var portNum = comboBox1.SelectedItem.ToString();
        using (SerialPort port = new SerialPort( portNum, 9600, Parity.None, 8))
        {
            byte[] bytesToSend = new byte[9] { 0x38, 0x30, 0x31, 0x73, 0x21, 0x30, 0x30, 0x31, 0x0D };
            port.Open();
            port.Write(bytesToSend, 0, 9);
        }
    }

    private void button2_Click(object sender, EventArgs e)
    {
        var portNum = comboBox1.SelectedItem.ToString();
        using (SerialPort port = new SerialPort( portNum, 9600, Parity.None, 8))
        {
            byte[] bytesToSend = new byte[9] { 0x38, 0x30, 0x31, 0x73, 0x21, 0x30, 0x30, 0x30, 0x0D };
            port.Open();
            port.Write(bytesToSend, 0, 9);
        }
    }

Upvotes: 4

Views: 816

Answers (4)

user27414
user27414

Reputation:

If your ComboBox is just displaying "COM1", etc, do this:

using (SerialPort port = new SerialPort(comboBox1.Text, 9600, Parity.None, 8))

Or, if you need to use SelectedItem,

using (SerialPort port = new SerialPort(comboBox1.SelectedItem.ToString(), 9600, Parity.None, 8))

If you really want a property,

string SelectedPort { get { return comboBox1.SelectedItem.ToString(); } }

Better yet, refactor your code to just specify the data in the button handler:

private void button1_Click(object sender, EventArgs e)
{
    byte[] bytesToSend = new byte[9] { 0x38, 0x30, 0x31, 0x73, 0x21, 0x30, 0x30, 0x31, 0x0D };
    this.Send(bytesToSend);
}

private void button2_Click(object sender, EventArgs e)
{
    byte[] bytesToSend = new byte[9] { 0x38, 0x30, 0x31, 0x73, 0x21, 0x30, 0x30, 0x30, 0x0D };
    this.Send(bytesToSend);
}

private void Send(byte[] bytesToSend)
{
    var portNum = comboBox1.SelectedItem.ToString();
    using (SerialPort port = new SerialPort( portNum, 9600, Parity.None, 8))
    {
        port.Open();
        port.Write(bytesToSend, 0, bytesToSend.Length);
    }
}

Upvotes: 4

Tony Hopkinson
Tony Hopkinson

Reputation: 20320

Disable Buttons 1 and 2 at design time.

add a private member PortNum

Add a SelectedItemChange Event handler to the combobox In that if the selection is not null, save it in PortNum and enable the buttons

Upvotes: 0

millimoose
millimoose

Reputation: 39950

Use a property:

// this is a class member
string PortNum 
{
    get { return comboBox1.SelectedItem.ToString(); }
}

// instead of your original code
using (var port = new SerialPort(PortNum, ...)) {
    ...
}

Upvotes: 0

Fede
Fede

Reputation: 44028

Create the property in the form scope:

public Form Form1
{
    public string PortNum {get;set;}

    public void ComboBox1_SelectionChanged(object sender, EventArgs e)
    {
       PortNum = ComboBox1.SelectedItem.ToString();
    }

    ... (rest of your code)

}

Upvotes: 2

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