Getting selected value of a combobox

Question

public class ComboboxItem { 
            public string Text { get; set; } 
            public string Value { get; set; }
            public override string ToString() { return Text; } 
        }

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            int selectedIndex = comboBox1.SelectedIndex;
            int selecteVal = (int)comboBox1.SelectedValue; 
            ComboboxItem selectedCar = (ComboboxItem)comboBox1.SelectedItem;
            MessageBox.Show(String.Format("Index: [{0}] CarName={1}; Value={2}", selectedIndex, selectedCar.Text, selecteVal));
        }

I'm adding them like:

ComboboxItem item = new ComboboxItem();
                    item.Text = cd.Name;
                    item.Value = cd.ID;
                    this.comboBox1.Items.Add(item);

I keep getting a NullReferenceExeption and not sure why. the text seems to show up just fine.

James Hill · Accepted Answer · 2011-08-01T16:09:18.810

51

Try this:

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
    ComboBox cmb = (ComboBox)sender;
    int selectedIndex = cmb.SelectedIndex;
    int selectedValue = (int)cmb.SelectedValue;

    ComboboxItem selectedCar = (ComboboxItem)cmb.SelectedItem;
    MessageBox.Show(String.Format("Index: [{0}] CarName={1}; Value={2}", selectedIndex, selectedCar.Text, selecteVal));        
}

edited Aug 01 '11 at 16:09

answered Aug 01 '11 at 16:00

James Hill

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8

I think that `ComboBoxItem` class is available only in WPF projects. – T30 Nov 24 '14 at 16:58
OP declared it in their post. Surprised there isn't one in the System.Windows.Forms namespace...or did I miss something? – AS7K Apr 01 '19 at 16:06

score 15 · Answer 2 · edited May 22 '18 at 12:54

You are getting NullReferenceExeption because of you are using the cmb.SelectedValue which is null. the comboBox doesn't know what is the value of your custom class ComboboxItem, so either do:

ComboboxItem selectedCar = (ComboboxItem)comboBox2.SelectedItem;
int selecteVal = Convert.ToInt32(selectedCar.Value);

Or better of is use data binding like:

ComboboxItem item1 = new ComboboxItem();
item1.Text = "test";
item1.Value = "123";

ComboboxItem item2 = new ComboboxItem();
item2.Text = "test2";
item2.Value = "456";

List<ComboboxItem> items = new List<ComboboxItem> { item1, item2 };

this.comboBox1.DisplayMember = "Text";
this.comboBox1.ValueMember = "Value";
this.comboBox1.DataSource = items;

Isn't there anyway to use comboBox.SelectedValue for a custom item without using a dataSource? Eg. if you use a datasource you can't remove or add an item to the combobox Items. — user3532232, May 09 '16 at 08:14

score 7 · Answer 3 · answered Feb 13 '14 at 21:22

I had a similar error, My Class is

public class ServerInfo
{
    public string Text { get; set; }
    public string Value { get; set; }
    public string PortNo { get; set; }

    public override string ToString()
    {
        return Text;
    }
}

But what I did, I casted my class to the SelectedItem property of the ComboBox. So, i'll have all of the class properties of the selected item.

// Code above
ServerInfo emailServer = (ServerInfo)cbServerName.SelectedItem;

mailClient.ServerName = emailServer.Value;
mailClient.ServerPort = emailServer.PortNo;

I hope this helps someone! Cheers!

score 1 · Answer 4 · answered Apr 05 '20 at 14:35

You have to cast the selected item to your custom class (ComboboxItem) Try this:

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
ComboBox cmb = (ComboBox)sender;
            int selectedIndex = cmb.SelectedIndex;
            string selectedText = this.comboBox1.Text;
            string selectedValue = ((ComboboxItem)cmb.SelectedItem).Value.ToString();

ComboboxItem selectedCar = (ComboboxItem)cmb.SelectedItem;
MessageBox.Show(String.Format("Index: [{0}] CarName={1}; Value={2}", selectedIndex, selectedCar.Text, selecteVal));

}

score 0 · Answer 5 · edited May 19 '15 at 11:24

0

Try this:

private void cmbLineColor_SelectedIndexChanged(object sender, EventArgs e)
    {
        DataRowView drv = (DataRowView)cmbLineColor.SelectedItem;
        int selectedValue = (int)drv.Row.ItemArray[1];
    }

edited May 19 '15 at 11:24

Marcus

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answered May 19 '15 at 11:12

Vikas4u

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score 0 · Answer 6 · edited Jul 28 '16 at 19:37

0

The problem you have with the SelectedValue is not converting into integer. This is the main problem so usinge the following code snippet will help you:

int selectedValue;
bool parseOK = Int32.TryParse(cmb.SelectedValue.ToString(), out selectedValue);

edited Jul 28 '16 at 19:37

help-info.de

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answered Jul 28 '16 at 17:20

Tariq Nawaz Khan

11
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score 0 · Answer 7 · edited Mar 03 '20 at 09:33

0

Try this:

int selectedIndex = comboBox1.SelectedIndex;
comboBox1.SelectedItem.ToString();
int selectedValue = (int)comboBox1.Items[selectedIndex];

edited Mar 03 '20 at 09:33

Community

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answered Nov 10 '18 at 14:23

Hakan Murat Aksüt

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OP had a C# question. Your answer looks like C++. – Adrian W Nov 10 '18 at 14:49

Getting selected value of a combobox

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