Looping through ComboBoxItems

Question

I want to select item in ComboBox with certain value. For this I created this method:

private int getIndex(ComboBox cb, string value)  
{  
            int index = 0;  
            int actual_index = 0;  
            foreach (ComboBoxItem item in cb.Items)  
            {  
                if (item.Tag.ToString() == value)  
                {  
                    actual_index = index;  
                }  
                index++;  
            }  
            return actual_index;  
}  

However, when I tried to run it, I got error

Unable to cast object of type System.String to type System.Windows.Controls.ComboBoxItem

(sorry if it is inaccurate, I translated it with Google Translate)

What am I doing wrong?

Answer 1

Since I don't know your data source here is an example of a mocked up ComboBox.

<Grid>  
    <StackPanel Margin="10,10,10,379">  
        <ComboBox x:Name="ComboBox1">  
            <ComboBoxItem Tag="First">  
                <StackPanel Orientation="Horizontal">  
                    <TextBlock Foreground="Red">Red</TextBlock>  
                </StackPanel>  
            </ComboBoxItem>  
            <ComboBoxItem Tag="Second">  
                <StackPanel Orientation="Horizontal">  
                    <TextBlock Foreground="Green">Green</TextBlock>  
                </StackPanel>  
            </ComboBoxItem>  
            <ComboBoxItem Tag="Third">  
                <StackPanel Orientation="Horizontal">  
                    <TextBlock Foreground="Blue">Blue</TextBlock>  
                </StackPanel>  
            </ComboBoxItem>  
        </ComboBox>  
    </StackPanel>  
    <Button  
        Margin="54,140,617,259"  
        Click="Button_Click"  
        Content="Button" />  
</Grid>  

Behind

using System;  
using System.Diagnostics;  
using System.Windows;  
using System.Windows.Controls;  
  
namespace WpfApp1  
{  
    public partial class MainWindow : Window  
    {  
        public MainWindow()  
        {  
            InitializeComponent();  
        }  
  
        private void Button_Click(object sender, RoutedEventArgs e)  
        {  
            var findValue = "second";  
            var index = getIndex(ComboBox1, findValue);  
            MessageBox.Show(index > -1 ? $"Index is {index} for '{findValue}'" : $"'{findValue}' Not found");  
        }  
        private int getIndex(ComboBox cb, string value)  
        {  
            int index = 0;  
  
            foreach (ComboBoxItem item in cb.Items)  
            {  
                if (item.Tag is string currenTagValue)  
                {  
                    if (string.Equals(currenTagValue, value, StringComparison.OrdinalIgnoreCase))  
                    {  
                        return index;  
                    }  
                }  
                  
                index++;  
            }  
  
            return -1;  
        }  
    }  
}