C# winform unable to cast object of type 'system.string' to type 'item'.

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I have a Project and getting this error. Unable to cast object of type 'System.String' to type 'Item'.

The error is on this line

var item = (Item)comboBox1.SelectedItem;

I have tried everything but the right thing.

full code

C#

<pre>public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            
        }

        

        private void Form1_Load(object sender, EventArgs e)
        {
            var itemList = new List<Item>()
            {
                new Item() { Text = "L", Value = 1.75M },
                new Item() { Text = "US fl oz", Value = 1.698M }
            };

            comboBox1.DataSource = itemList;
            comboBox1.DisplayMember = "Text";
            comboBox1.ValueMember = "Value";

            comboBox2.DataSource = itemList;
            comboBox2.DisplayMember = "Text";
            comboBox2.ValueMember = "Value";
        }


        private void button1_Click(object sender, EventArgs e)
        {
            if (comboBox1.SelectedItem != null)
            {
                var item = (Item)comboBox1.SelectedItem;
                MessageBox.Show($"{item.Text} - {item.Value}");


                textBox4.Text = ((Convert.ToDouble(textBox2.Text) / Convert.ToDouble(textBox3.Text)
                - Convert.ToDouble(textBox10.Text)) * Convert.ToDouble(textBox1.Text) / Convert.ToDouble(comboBox1.SelectedItem)).ToString("0.00");


            }
        }

What I have tried:

lots of looking on the internet and other program code

Posted 13-Dec-17 12:01pm

Member 12349103

Updated 13-Dec-17 22:17pm

Oshtri Deka

v2

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Comments

Karthik_Mahalingam 13-Dec-17 22:58pm

show the Item class code

1 solution

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an0ther1 · Accepted Answer · 2017-12-13T12:35:00

The Property SelectedItem does not return an Item, it returns an Object. MSDN reference for the SelectedItem property - MSDN - ComboBox.SelectedItem Property[^]
You could change your code as follows;

C#

// current text value
string strItemText = comboBox1.Text;
// convert the selected value to a Decimal value - always use TryParse & handle errors
decimal decItemValue;
if(!Decimal.TryParse(comboBox1.SelectedValue.ToString(), out decItemValue))
{ // invalid value - handle error
}

Use your debugger, between reference information - MSDN is great but there are others - and your debugger you will learn more about coding than you think

Your code;

C#

var item = (Item)ComboBox.SelectedItem;

is attempting to unbox an object to a value type, this only works for explicit conversions, if the conversion is not explicit then the conversion will fail - refer; Boxing and Unboxing (C# Programming Guide) | Microsoft Docs[^]

C# is a type-strong language & you should use the correct type for variables - IMO. In this case I would see the variable type "var" and assume you were being lazy. There is a use for the var type but this is not it - refer; var (C# Reference) | Microsoft Docs[^]

Kind Regards