InvalidArgument=“0”的值对“SelectedIndex”无效。 参数名称：SelectedIndex

Question

I am getting the above error when i am trying this code. I tried giving just my code but no use. (It was default)

Here is my XML file

The error is in cmbProduct_SelectedIndexChanged event.

        cmbProduct --> combobox
        cmbBrand   --> combobox

Global

        DataSet dsUpdate = new DataSet();

Form_load

        dsUpdate.ReadXml(@"...\..\stock.xml");
        cmbProduct.DataSource = dsUpdate.Tables[0]
            .DefaultView.ToTable(true, "productname");//.DefaultView;
        cmbProduct.DisplayMember = "productname";
        cmbProduct.SelectedIndex = 0;

cmbProduct_SelectedIndexChanged

        cmbBrand.Items.Clear();
        foreach (DataRow Row in dsUpdate.Tables[0].Select("productname='" + cmbProduct.Text + "'"))
        {
            //cmbBrand.SelectedIndex = i;
            cmbBrand.Items.Add(Row["brandname"].ToString());
            //i++;
        } 
        cmbBrand.SelectedIndex = 0; /*ERROR*/  

Please help
Thanks in Advance.

Answer 1

Problem is:

when you start application, you do not have items in cmbBrand, but cmbProduct fires SelectedIndexChanged.

Try this:

remove SelectedIndexChanged event initialization from Form1.Designer.cs. Try to find following line:

this.cmbProduct.SelectedIndexChanged += new System.EventHandler(this.cmbProduct_SelectedIndexChanged);

After that, when you populate DataSet with data from xml file, initialize SelectedIndexChanged event:

dsUpdate.ReadXml(@"...\..\stock.xml");
cmbProduct.DataSource = dsUpdate.Tables[0].DefaultView.ToTable(true, "productname");//.DefaultView;
cmbProduct.DisplayMember = "productname";
this.cmbProduct.SelectedIndexChanged += new System.EventHandler(this.cmbProduct_SelectedIndexChanged);
cmbProduct.SelectedIndex = 0;

Answer 2

i had same error. i think this error have a some reasons. so my error is related to "set DataSource in another thread is not working"

example

//Run in another thread
myComboBox.DataSource = myDataSource; //not set

fix with

myComboBox.Invoke(new Action(() => myComboBox.DataSource = myDataSource));

Answer 3

You can also try this. Before setting combobox DataSource set its BindingContext

cmbProduct.BindingContext = this.BindingContext;

Answer 4

This will happen if you attempt to set the SelectedIndex while there is no valid datasource. If you're resetting the default to 0, and occasionally changing the datasource list, you may see this. You don't need to default to 0 if applying a new datasource, so simple check will avoid it happening:

if (comboBox.Datasource != null) comboBox.SelectedIndex = 0;

Answer 5

If you have this issue:

• use the Form_Activated event handler to control setting the indexes.
• For me, I had a series of dynamically generated ComboBoxes I added to a Form.
• I made a list of the ones where I wanted to use SetIndex=0, then iterated through them in this handler.
• I also had a boolean, firstFormActivation, when called the SetIndex the one time only..
• You can incidentally use this method for Focus() too, so first field in a Form gets focus when dynamically added.

Here is some code to illustrate the point:

    private readonly List<ComboBox> combosToSetIndexOn = new List<ComboBox>();
    private bool firstActivation = true;
    private Control firstWindowsControl = null;

    ...
    // Other code sets firstWindowsControl...

    private void DynamicForm_Activated(object sender, EventArgs e)
    {
        if (firstActivation)
        {
            firstActivation = false;
            bool fwcPresent = (firstWindowsControl != null);
            Console.WriteLine($"DynamicForm_Activated: firstWindowControl present: {fwcPresent}");
            if (fwcPresent)
            {
                firstWindowsControl.Focus();
            }

            if (combosToSetIndexOn.Count > 0)
            {
                foreach (ComboBox c in combosToSetIndexOn)
                {
                    Console.WriteLine($"DynamicForm_Activated: processing: {c.Name}");
                    c.SelectedIndex = 0;
                }
            }
        }

Answer 6

In my case the following was causing my problem

myComboBox.DataSource = myBindingSource
myBindingSource.DataSource = items.ToList()  // error

The following worked

myComboBox.DataSource = null;
myBindingSource.DataSource = items.ToList();
MyComboBox.DataSource = myBindingSource;