Question

Combobox从SQL数据库中提取名称列，但是在选中时，我需要将dentist列表中的其他属性填充到标记为TextBoxes的内容中。

在If语句中，我收到错误，突出显示的代码为dent.Name。错误如下：

描述：不能隐式转换类型＆＃39;字符串＆＃39;到＆＃39; int＆＃39;

namespace DentistSurgery
{
    public partial class Dentist_Info : Form
    {
        Surgery mySurgery = new Surgery();
        public SqlCommand SelectCommand;
        private SqlDataAdapter da;
        DataRow dr;
        Surgery _formsSurgery;        

        public Dentist_Info(Surgery SurgeryToDisplay)
        {    
            _formsSurgery = SurgeryToDisplay;                
        }

        public void FillCombo()
        {
            using (SqlConnection conn = new SqlConnection(@"Data Source = GGJG; Initial Catalog = DentistDB; Integrated Security = True"))
            {
                SqlCommand SelectCommand = new SqlCommand("SELECT * FROM DentistInfo", conn);
                conn.Open();
                DataSet ds = new DataSet();
                SqlDataAdapter da = new SqlDataAdapter(SelectCommand);
                da.Fill(ds);

                foreach (DataRow dr in ds.Tables[0].Rows)
                {
                    comboBox1.Items.Add(dr["DentistName"].ToString());
                }
                //conn.Close();
            }
        }

        public Dentist_Info()
        {
            InitializeComponent();
            FillCombo();        
        }

        public void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            List<Dentist> dentistList = new List<Dentist>();
            Dentist dent = new Dentist();

            if (comboBox1.SelectedIndex = dent.Name)
            {
                txtDName.Text = dent.Name.ToString();
                txtDSurname.Text = dent.Surname;
                txtDDOB.Text = dent.DOB.ToString();
                txtGender.Text = dent.Gender;
                txtSalary.Text = dent.Salary.ToString(); 
            }
        }

Answer 1

您没有使用相等运算符（==）。您正在使用赋值运算符（=）。因此，你得到错误的原因......

"Cannot implicitly convert type 'string' to 'int' DentistSurgery"

因为您尝试将所选索引（类型为int）分配给字符串。

这意味着您应该使用comboBox1.SelectedValue（字符串类型）。然后你可以使用相等运算符（==）比较像这样的值......

if (comboBox1.SelectedValue == dent.Name)
{
    // Do stuff here.
}

Answer 2

dent是新的空对象。 dent.Name为空string，您无法将string隐式转换为integer SelectedIndex。

修改：由于其他问题（和其他问题），这里有更多的代码。

因此，您的dentistList为空，dentist也为空。在这种情况下，将牙医与所选项目进行比较是没有用的。尝试像这样重新安排代码。我还添加了一些评论：

//I'm assuming this is form public partial class Dentist_Info : Form { //create list of dentists here, so that it is visible thru whole form. private List<Dentist> dentistList = new List<Dentist>(); public Dentist_Info(Surgery SurgeryToDisplay) { _formsSurgery = SurgeryToDisplay; } public void FillComboAndListOfDentists() { using (SqlConnection conn = new SqlConnection(@"Data Source = GGJG; Initial Catalog = DentistDB; Integrated Security = True")) { SqlCommand SelectCommand = new SqlCommand("SELECT * FROM DentistInfo", conn); conn.Open(); DataSet ds = new DataSet(); SqlDataAdapter da = new SqlDataAdapter(SelectCommand); da.Fill(ds); foreach (DataRow dr in ds.Tables[0].Rows) { comboBox1.Items.Add(dr["DentistName"].ToString()); // creating new dentist Dentist dent = new Dentist(); dent.Name = dr["DentistName"].ToString(); dent.Surname = dr["DentistSurname"].ToString(); //etc... //add dentist to list dentistList.Add(dent); } //conn.Close(); } } public Dentist_Info() { InitializeComponent(); FillComboAndListOfDentists(); } public void comboBox1_SelectedIndexChanged(object sender, EventArgs e) { //use LINQ to find specific dentist in the list (btw, you should use something unique, some kind of ID, not just Name Dentist dent = dentistList.FirstOrDefault(d => d.Name == comboBox1.SelectedValue); // once you have your dentist, fill all the details... if (dent != null) { txtDName.Text = dent.Name.ToString(); txtDSurname.Text = dent.Surname; txtDDOB.Text = dent.DOB.ToString(); txtGender.Text = dent.Gender; txtSalary.Text = dent.Salary.ToString(); } } }

Answer 3

SelectedIndex属性的类型为int，您希望将其与字符串值进行比较。您需要使用ToString()方法将其转换为字符串，您还应该在==语句中使用等于运算符=而不是赋值运算符if，如下所示：

if (comboBox1.SelectedIndex.ToString() == dent.Name)
{
    ....

但基于dent.Name，我认为您应该在此使用SelectedItem属性，但因为SelectedItem类型为object，您应该使用ToString()：< / p>

if (comboBox1.SelectedItem.ToString() == dent.Name)
{
   ...

Answer 4

更好的方法是使用selected Value从comboBox获取comboBox1.SelectedValue，然后将其与dentName进行比较。

public void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
    {
        List<Dentist> dentistList = new List<Dentist>();
        Dentist dent = new Dentist();


       if (comboBox1.SelectedValue == dent.Name)
        {
            txtDName.Text = dent.Name.ToString();
            txtDSurname.Text = dent.Surname;
            txtDDOB.Text = dent.DOB.ToString();
            txtGender.Text = dent.Gender;
            txtSalary.Text = dent.Salary.ToString();

        }


    }

从ComboBox中选择时，无法填充列表集合

4 个答案: