将数据读取到数组，然后在C＃中填充到ComboBox

Question

I have user data (name, username, image) in a database and I need to list the name and id in a combo box. When an item in the combo box is selected it should display a picture. I have created a User and a UserDB class. In my User class I have the following code:

public class User
  {
    private String u_firstname;
    private String u_lastname;
    private String u_username = string.Empty;
    private Byte [] u_image;
    private Byte [] u_template;


    public User(OleDbDataReader dr)
    {            
        u_firstname = dr["USER_FIRST_NM"].ToString();
        u_lastname = dr["USER_LAST_NM"].ToString();
        u_username = dr["USER_NAME"].ToString();
        u_image = (Byte [])dr["USER_IMAGE"];
        u_template = (Byte [])dr["USER_TEMPLATE"];

    }
}

In my UserDB class I have the following code:

public class UserDB
 {
    public static String workingDirectory = System.IO.Directory.GetCurrentDirectory();
    public static String dbProvider = "Microsoft.ACE.OLEDB.12.0";
    public static String dbName = "Users_DB.accdb";        
    public static String dbConnString = String.Format(@"Provider={0};Data Source={1}\Data\{2}", dbProvider, workingDirectory, dbName);


    public User[] usersInDatabaseList()
    {
        User u;
        List<User> clist = new List<User>();

        OleDbConnection cn = new OleDbConnection(dbConnString);

        String strSQL = "SELECT USER_FIRST_NM, USER_LAST_NM, USER_NAME, USER_IMAGE, USER_TEMPLATE FROM KF001_USERS";

        OleDbCommand cm = new OleDbCommand(strSQL, cn);
        OleDbDataReader dr;

        cn.Open();

        dr = cm.ExecuteReader(CommandBehavior.CloseConnection);

        while (dr.Read())
        {                
            u = new User(dr);
            clist.Add(u);
        }

        cn.Close();


        return clist.ToArray();
    }
}

and on my mainForm I have the following method that I am using for my combo-box:

public void FillDropDownList()
    {
        try
        {

            //int i;
            UserDB db = new UserDB();
            User[] userList = db.usersInDatabaseList();

            comboBoxUsersEnrolled.Items.AddRange(userList);
            comboBoxUsersEnrolled.DisplayMember = ?      
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }
}

I am at a total loss as to how to get my database values to be displayed in the combobox. I'm also unsure of how to display a picture when an Item is selected. Can anyone help or steer me in the right direction please.

So I changed filldropdownlist method to the following:

 public void FillDropDownList()
    {

            UserDB db = new UserDB();
            User[] userList = db.cList();



            for (int i = 0; i < userList.Length; i++)
            {

                comboBoxUsersEnrolled.Items.Add(userList[i]);
                comboBoxUsersEnrolled.DisplayMember = "ComboName";




                if (comboBoxUsersEnrolled.SelectedIndex > 0 )
                {

                    byte[] pictureByteReader = (userList[i].UserImage);
                    MemoryStream ms = new MemoryStream(pictureByteReader);
                    Image picture = Image.FromStream(ms);
                    picBoxCapture.Image = picture;
                }

            }


    }

I'm trying to add to my combobox and at the same time send a picture to a picturebox if that item is selected. My code does nothing. Gives no errors or anything. Help!

Answer 1

You have done most of the work already.

The DisplayMember property that you've marked with ? indicates the property that should be used to display in the ComboBox. Your class doesn't have any properties - it only has fields - so first you'll want to create a property

public class User
{
    // all your existing fields

    public string Name
    {
        get
        {
            return this.u_username;
        }
    }

Then you can set the DisplayMember = "Name"; to use the Name as the display property.

Using an image requires more work - you will need to use a template in the combobox instead of a string. Try googling that to find an example.