C# 如何将列表中的一个值返回到 ComBox 中？ 而不是所有

Question

I am aiming to return a single value of CustomerName into a ComboBox.

This is how I get the data from the database:

public class DataAccess
{
    public List<ComplaintModel> FindOrderNumber(string orderNumber)
    {
        using(SqlConnection conn = new SqlConnection(ConnectionString.MJMconnString))
        {
            var output = conn.Query<ComplaintModel>($@"
                    SELECT 
                    TRIM(p.description) as Product,
                    c.name AS CustomerName,
                    FROM SalesOrder so JOIN SalesOrderLine sol ON
                    so.id = sol.salesOrderID JOIN Customer c ON
                    so.customerID = c.id JOIN Product p ON
                    sol.productID = p.id WHERE so.number = '{orderNumber}'").ToList();
            return output;
        }
    }
}

This would be the output (Used Excel to show you a rough idea):

So the ComboBoxes would look like this:

Quick conclusion

The customer name will always be the same for specific OrderNumber but products vary.

Form

Within my form I load the Product and Customer combo-box. ( Note: I know you may be thinking to use a TextBox instead of a ComboBox for Customer , it just needs to be).

List<ComplaintModel> OrderNumber = new List<ComplaintModel>();

public void searchButton_Click(object sender, EventArgs e)
{
    clearBindings();

    DataAccess db = new DataAccess();
     
    // Search Order Number that is specified in a text box
    OrderNumber = db.FindOrderNumber(orderNumber.Text);
  
    // List all products
    product.DataSource = OrderNumber;
    product.DisplayMember = "Product";

    // Show customer name - but as [0] instead of all.
    customer_name.DataSource = OrderNumber;
    customer_name.DisplayMember = "CustomerName";
    

}

Desired output of combobox

This is my model

public class ComplaintModel
{
    public string CustomerName { get; set; }
    public string Product { get; set; }
}

Question

How do I retrieve just a single value of CustomerName into the ComboBox?

Answer 1

You need to create: Customer class, Order class.

Then You need to Create two lists for two comboboxes: List<Customer> customers for customer combobox List<Order> orders for orders combobox to show orders for selected customer (on combobox change event).

public class Customer
{
public string Id {get;set;}
public string Name {get;set;}
public List<Order> Orders {get;set;}
}

public class Order
{
public string Id {get;set;}
public string Name {get;set;}
public int CustomerId {get;set;}
}