從組合框中選擇時無法填充列表集合

Question

Combobox從SQL數據庫中提取名稱列，但是選中時需要將dentist列表中的其他屬性填充到標記爲TextBoxes的列表中。

在If聲明是我得到的錯誤，突出顯示的代碼是dent.Name。錯誤如下：

描述：無法隱式轉換類型 '字符串' 到 '廉政'

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

的SelectedIndex屬性是int類型的，你想它有一個字符串值進行比較。您需要使用ToString()方法將其轉換爲字符串，你也應該使用賦值運算符=平等操作==，而不是在你的if聲明是這樣的：

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

但基於dent.Name我認爲你應該在這裏使用SelectedItem屬性但同樣因爲SelectedItem的類型爲object你應該使用ToString()：

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

Answer 2

dent是新的，空的對象。 dent.Name給出空string，並且不能將隱式轉換爲string至integer即SelectedIndex。

編輯： 由於其他問題（和其他問題），這裏是更多的代碼。

因此，您的dentistList爲空，並且dentist也爲空。在這種情況下，比較牙醫與選定的項目是沒有用的。 嘗試像這樣重新排列你的代碼。我還添加了一些評論：

//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

您沒有使用等號運算符（==）。您正在使用賦值運算符（=）。因此，爲什麼你的錯誤......

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

因爲你要選擇的指標（這是int型）將一個字符串賦值。

這意味着你應該使用comboBox1.SelectedValue（它是字符串類型）。然後你可以使用等號（= =）的值進行比較是這樣的...

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

Answer 4

一個更好的辦法是讓selected Value˚F從comboBox使用comboBox1.SelectedValue，然後將其與dentName進行比較。

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(); 

     } 


    }