C＃-用MySql数据库填充ComboBox的意外结果

Question

I my class DBConnect , I have this function to populate a ComboBox to database based on input query:

public void POPULATE_COMBOBOX(string query, ComboBox myComboBox)
{
    if (this.OpenConnection() == true)
    {
        MySqlCommand cmd = new MySqlCommand(query, connection);

        MySqlDataAdapter adapter = new MySqlDataAdapter(cmd);
        DataTable myDataTable = new DataTable();

        adapter.Fill(myDataTable);
        myComboBox.DataSource = myDataTable; 

        this.CloseConnection();
    }
}

And here's how I use it

DBConnect.POPULATE_COMBOBOX("SELECT NAME FROM users", comboBox_Name);

I have 3 rows in column NAME , and I expect those 3 names will be displayed in my comboBox_Name . However instead, I got 3 lines of System.Data.DataRowView in my combobox. Any idea how to convert those DataRowView to string?

Answer 1

You have to tell combobox what column to display.

//Preparation
var dt = new DataTable();
dt.Columns.Add("Name", typeof(string));
dt.Rows.Add("Name1");
dt.Rows.Add("Name2");

//Setup data binding
myComboBox.DataSource = dt.DefaultView;
myComboBox.DisplayMember = "Name";
myComboBox.ValueMember = "Name";

Then SelectedItem gets the actual ComboBox item (in this case a DataRowView), whereas SelectedValue gets the value of the property you specified as the ValueMember of the ComboBox

Or another way how to populate your ComboBox is:

MySqlDataReader sqlReader = cmd.ExecuteReader();

while (sqlReader.Read())
{
    myComboBox.Items.Add(sqlReader["Name"].ToString());
}

sqlReader.Close();