How to get value of checked item from CheckedListBox?

You can iterate over the CheckedItems property:

foreach(object itemChecked in checkedListBox1.CheckedItems)
{
    MyCompanyClass company = (MyCompanyClass)itemChecked;    
    MessageBox.Show("ID: \"" + company.ID.ToString());
}

http://msdn.microsoft.com/en-us/library/system.windows.forms.checkedlistbox.checkeditems.aspx

Cast it back to its original type, which will be a DataRowView if you're binding a table, and you can then get the Id and Text from the appropriate columns:

foreach(object itemChecked in checkedListBox1.CheckedItems)
{
     DataRowView castedItem = itemChecked as DataRowView;
     string comapnyName = castedItem["CompanyName"];
     int? id = castedItem["ID"];
}

EDIT: I realized a little late that it was bound to a DataTable. In that case the idea is the same, and you can cast to a DataRowView then take its Row property to get a DataRow if you want to work with that class.

foreach (var item in checkedListBox1.CheckedItems)
{
    var row = (item as DataRowView).Row;
    MessageBox.Show(row["ID"] + ": " + row["CompanyName"]);
}

You would need to cast or parse the items to their strongly typed equivalents, or use the System.Data.DataSetExtensions namespace to use the DataRowExtensions.Field method demonstrated below:

foreach (var item in checkedListBox1.CheckedItems)
{
    var row = (item as DataRowView).Row;
    int id = row.Field<int>("ID");
    string name = row.Field<string>("CompanyName");
    MessageBox.Show(id + ": " + name);
}

---

You need to cast the item to access the properties of your class.

foreach (var item in checkedListBox1.CheckedItems)
{
    var company = (Company)item;
    MessageBox.Show(company.Id + ": " + company.CompanyName);
}

Alternately, you could use the OfType extension method to get strongly typed results back without explicitly casting within the loop:

foreach (var item in checkedListBox1.CheckedItems.OfType<Company>())
{
    MessageBox.Show(item.Id + ": " + item.CompanyName);
}