c# - 我的 ComboBox3 无法将第二个数据类型转换为我的 textbox1

Question

大家好晚上好:D为什么我的另一个数据类型不能转换为textbox1.text我不知道为什么他不能转换但我的其他数据是正确的这是我的代码 DATABASE

       private void AddEmployee_Load(object sender, EventArgs e)
    {
        fillposition();
    }
//fill
    public void fillposition()
    {
        con.Open();
        MySqlDataReader dr;
        MySqlCommand cmd = new MySqlCommand("select * from position", con);
        dr = cmd.ExecuteReader();

        while (dr.Read())
        {
            string data = dr.GetString("EmpPosition");
            comboBox3.Items.Add(data);
        }
        con.Close();
    }

Form did not cast the prefix

    public void getposition()
    {
        if (Int32.TryParse(comboBox3.SelectedItem.ToString(), out tc))
        {
            con.Open();
            MySqlCommand cmd = new MySqlCommand("select * from position 
            where EmpPosition=@EmpPosition ", con);
            cmd.Parameters.Add("@EmpPosition", MySqlDbType.Int32).Value = 
            tc;
            dr = cmd.ExecuteReader();
            if (dr.Read())
            {
                textBox1.Text = dr["Prefix"].ToString();
            }
            con.Close();
        }
    }
   private void comboBox3_SelectedIndexChanged_1(object sender, EventArgs e)
    {
        getposition();
    }

Answer 1

1) 设置组合框 ValueMember 和 DisplayMember 属性。

public void fillposition()
{
    //Your code as it is
    con.Close();

    comboBox3.ValueMember = "Value";
    comboBox3.DisplayMember = "Text";
}

2) 然后在下面的if

中使用SelectedValue代替SelectedItem

if (Int32.TryParse(comboBox3.SelectedValue.ToString(), out tc))
{
   //You stuff here
}