問題與方法

Question

我有另一個問題。我的方法：

public StudentProfile GetFullStudentProfile(int userID) 
{ 
    SqlConnection conn = new SqlConnection(Config.DbConnectionString); 
    SqlCommand cmd = new SqlCommand("GetFullUserProfile", conn); 
    cmd.CommandType = CommandType.StoredProcedure; 

    cmd.Parameters.Add(new SqlParameter("@UserID", SqlDbType.Int)); 
    cmd.Parameters["@UserID"].Value = userID; 
    StudentProfile sp = null; 
    try 
    { 
     conn.Open(); 
     SqlDataReader reader = cmd.ExecuteReader(CommandBehavior.SingleRow); 

     if (reader.Read()) 
     { 
      sp = new StudentProfile((int)reader["UserID"], (string)reader["UserName"], (string)reader["UserFamilyName"], (DateTime)reader["UserBirthDay"], (string)reader["UserTelephone"], (string)reader["UserEmail"], (DateTime)reader["UserRegDate"], (string)reader["UserComment"], (bool)reader["UserActive"]); 
     } 

     reader.Close(); 

    } 
    catch (Exception ex) 
    { 
     //lbl.Text = ex.Message; 
    } 
    finally 
    { 
     conn.Close(); 
    } 
    return sp; 
} 

守則WebUserControl：

protected void ddlStudents_SelectedIndexChanged(object sender, EventArgs e) 
{ 
    CatalogAccess ca=new CatalogAccess(); 
    lblEmail.Visible = true; 
    lblName.Visible = true; 

    lblTelephone.Visible = true; 
    HiddenID.Value = ddlStudents.SelectedValue; 
    lblName.Text = HiddenID.Value; 
    lblEmail.Text = ca.GetFullStudentProfile(ddlStudents.SelectedIndex).UserEmail; 
    lblFamilyName.Visible = true; 
    lblBirth.Visible = true; 
    ddlStudents.Items.Clear(); 
    PopulateStudentsDDL(); 

} 

當我運行的代碼我得到異常

難道我的理解對不對，這個問題是在方法GetFullStudentProfile（）？如果是這樣，那該如何解決？

我認爲這個問題是：

StudentProfile sp = null; 

所以說，SP變量沒有填充在try塊數據。是嗎？

現在加入StudentProfile.cs類上市：

public class StudentProfile 

{ 公共StudentProfile（INT用戶ID，用戶名字符串，字符串userFamilyName，日期userBirthDay，串userTelephone，串USEREMAIL，日期userRegDate，串UserComment在，布爾userActive） { UserID = userID; UserName = userName; UserFamilyName = userFamilyName; UserBirthDay = userBirthDay; UserTelephone = userTelephone; UserEmail = userEmail; UserRegdate = userRegDate; UserComment = userComment; UserActive = userActive; }

public int UserID 
{ 
    get; 
    set; 
} 

public string UserName 
{ 
    get; 
    set; 
} 

public string UserFamilyName 
{ 
    get; 
    set; 
} 

public DateTime UserBirthDay 
{ 
    get; 
    set; 
} 

public string UserTelephone 
{ 
    get; 
    set; 
} 

public string UserEmail 
{ 
    get; 
    set; 
} 

public DateTime UserRegdate 
{ 
    get; 
    set; 
} 

public string UserComment 
{ 
    get; 
    set; 
} 

public bool UserActive 
{ 
    get; 
    set; 
} 

}

Answer 1

好的。我做了一個新的方法：

public UserDetails GetUser(int userID) 
{ 
    SqlConnection conn = new SqlConnection(Config.DbConnectionString); 
    SqlCommand cmd = new SqlCommand("GetFullUserProfile", conn); 
    cmd.CommandType = CommandType.StoredProcedure; 
    cmd.Parameters.Add(new SqlParameter("@UserID", SqlDbType.Int, 4)); 
    cmd.Parameters["@UserID"].Value = userID; 
    try 
    { 
     conn.Open(); 
     SqlDataReader reader = cmd.ExecuteReader(CommandBehavior.SingleRow); 
     // Check if the query returned a record. 
     if (!reader.HasRows) return null; 
     // Get the first row. 
     reader.Read(); 
     UserDetails emp = new UserDetails((int)reader["UserID"], (string)reader["UserName"], (string)reader["UserFamilyName"], (DateTime)reader["UserBirthDate"], (string)reader["UserTelephone"], (string)reader["UserEmail"], (DateTime)reader["RegDate"], (string)reader["UserComment"], (int)reader["UserActive"]); 
     reader.Close(); 
     return emp; 
    } 
    catch (SqlException err) 
    { 
     throw new ApplicationException("Data error."); 
    } 
    finally 
    { 
     conn.Close(); 
    } 
} 

新類：

using System; 

public class UserDetails 
{ 
    public UserDetails(int userID, string userName, string userFamilyName, DateTime userBirthDate, string userTelephone, string userEmail, DateTime regDate, string userComment, int userActive) 
    { 
     UserID = userID; 
     UserName = userName; 
     UserFamilyName = userFamilyName; 
     UserBirthDay = userBirthDate; 
     UserTelephone = userTelephone; 
     UserEmail = userEmail; 
     RegDate = regDate; 
     UserComment = userComment; 
     userActive = UserActive; 
    } 

    public int UserID 
    { get; set; } 

    public string UserName 
    { get; set; } 

    public string UserFamilyName 
    { get; set; } 

    public DateTime UserBirthDay 
    { get; set; } 

    public string UserTelephone 
    { get; set; } 

    public string UserEmail 
    { get; set; } 

    public DateTime RegDate 
    { get; set; } 

    public string UserComment 
    { get; set; } 

    public int UserActive 
    { get; set; } 
} 

後，在WebUserControl我的背碼：

UserDetails ud = ca.GetUser(24); 
    //HiddenID.Value = String.Format(ud.UserID); 
    lblName.Text = ud.UserName; 
    lblEmail.Text = ud.UserEmail; 
    lblFamilyName.Text = ud.UserFamilyName; 
    lblBirth.Text=String.Format("{0:dd/MM/yyy}",ud.UserBirthDay); 
    lblTelephone.Text = ud.UserTelephone; 

，並得到了方法奏效。所以，這個階段已經準備好了。感謝所有幫助過我的人。線程關閉。

Answer 2

究竟什麼是空？我打賭GetFullStudentProfile方法返回null。

Answer 3

是的，這正是發生了什麼事。沒有找到學生匹配通過的ID。我會做下面的客戶端代碼：

StudentProfile sp=ca.GetFullStudentProfile(ddlStudents.SelectedIndex); 
lblEmail.Text = sp != null ? sp.UserEmail : string.Empty; 

此外，我將在GetFullStudentProfile方法的讀者操作改寫爲這樣的：

conn.Open(); 
SqlDataReader reader = cmd.ExecuteReader(CommandBehavior.SingleRow); 

if (reader.Read()) 
{ 
    sp = new StudentProfile((int)reader["UserID"], (string)reader["UserName"], (string)reader["UserFamilyName"], (DateTime)reader["UserBirthDay"], (string)reader["UserTelephone"], (string)reader["UserEmail"], (DateTime)reader["UserRegDate"], (string)reader["UserComment"], (bool)reader["UserActive"]); 
} 

reader.Close(); 

這只是改頭換面的常規，看起來更好恕我直言

Answer 4

另外：

HiddenID.Value = ddlStudents.SelectedValue; 
lblName.Text = HiddenID.Value; 

我y中發現這個名字設爲1時我們的汽車所以我覺得你其實是意味着將其設置爲：

lblName.Text = ddlStudents.SelectedValue; 

我不認爲設置等於本身的價值是要你以任何方式受益。檢查你的數據庫，UserEmail的列是否允許可空？

此外，在您的數據庫中，我相信UserID從1開始遞增，正確嗎？ SelectedIndex，我相信，從0開始。您可能需要將selectedvalue項目遞增1。

我只是看着你的另一個問題（http://stackoverflow.com/questions/5745820/assign-list-member-to-label），我覺得我有更多的信息在這裏。

如果你的數據庫不允許空類型，我會改變：

CatalogAccess ca=new CatalogAccess(); 
lblEmail.Visible = true; 
lblName.Visible = true; 

lblTelephone.Visible = true; 
HiddenID.Value = ddlStudents.SelectedValue; 
lblName.Text = HiddenID.Value; 
lblEmail.Text = ca.GetFullStudentProfile(ddlStudents.SelectedIndex).UserEmail; 
lblFamilyName.Visible = true; 
lblBirth.Visible = true; 
ddlStudents.Items.Clear(); 
PopulateStudentsDDL(); 

到：

CatalogAccess ca=new CatalogAccess(); 
lblEmail.Visible = true; 
lblName.Visible = true; 

lblTelephone.Visible = true; 

// if your table's ID increments starting at 0, otherwise ddlStudents.SelectedIndex + 1 
StudentProfile student = GetFullStudentProfile(ddlStudents.SelectedIndex); 

if (student != null) 
{ 
    lblName.Text = student.UserName; 
    lblEmail.Text = student.UserEmail; 
    //rest of the labels going here (I only see Name and Email) 
} 

... 

您也可以考慮把你的電話撥打SP的內側看到標籤=無條件，以便只有當有效的人員顯示時纔會顯示這些標籤。否則，把它們放在它之前。

否則我會做類似迪米特里說

lblName.Text = student.UserName != null ? student.UserName : String.Empty; 
lblEmail.Text = student.UserEmail != null ? student.UserEmail : String.Empty; 
// etc. 

如果nullables是可能的，學生對象實際上可以被分配到，但性能可能不是它在運行時可能導致應用程序的問題。