C# 将数据库中的多个数据项检索到一个标签中

我想从数据库中检索多个值并显示在一个标签上

我目前的数据库设计是：

courseid  scholarshipid  course
--------------------------------
    1           1        maths
    2           1        english
    3           1        science

scholarshipid   schName    
-----------------------
      1         moon 
      2         start
      3         light

我希望将此信息检索到单个标签中，例如

Maths, English, Science

然而，现在我设法找回了其中一个，那就是数学

这是我在代码隐藏中的代码：

protected void btnShowDetails_Click(object sender, EventArgs e)
{
    string Selectedid = GVFBAcc.SelectedRow.Cells[1].Text;//get user id
    int selectedIdtoPass = Convert.ToInt32(Selectedid);

    courseBLL getRecord = new courseBLL();
    addcourse courseRetrieve = new addcourse();
    courseRetrieve = getRecord.getCourseDetail(selectedIdtoPass);

    lbCourse.Text = courseRetrieve.course1 + "," + courseRetrieve.course1;
}

protected void btnShowDetails_Click(object sender, EventArgs e)
{
    string Selectedid = GVFBAcc.SelectedRow.Cells[1].Text;//get user id
    // Make sure this is the scholarshipid or the whole thing will
    // not work.
    int selectedIdtoPass = Convert.ToInt32(Selectedid);

    courseBLL courseRetriever = new courseBLL();

    // Remember you will get a list here
    List<addcourse> courses = courseRetriever.getCourseDetail(selectedIdtoPass);

    // This will take the list and separate the course property with a comma and space
    var courseNames = string.Join(", ", courses);

    // Now assign it to the text property
    lbCourse.Text = courseNames;
}

在我的课程中

public addcourse getCourseDetail(int idcourse)
{
        addcourse userObj = new addcourse();
        courseDAL objtoPass = new courseDAL();
        userObj = objtoPass.displayCourseInfo(idcourse);
        return userObj;
}

在我心中

public addcourse displayCourseInfo(int idcourse)
{
        string strCommandText = "Select course from course where schokarshipid = @schokarshipid";

        SqlCommand cmd = new SqlCommand(strCommandText, conn);
        cmd.Parameters.AddWithValue("@scholarshipid", idcourse);

        conn.Open();

        SqlDataReader myReader = cmd.ExecuteReader();
        addcourse userObj = new addcourse();

        while (myReader.Read())
        {
            int sID = Convert.ToInt32(myReader["courseID"].ToString());

            string course = myReader["course"].ToString();

            userObj = new addcourse(sID, course);
        }

        myReader.Close();
        return userObj;
}

编辑：

public addcourse displayCourseInfo(int idcourse)
{
        var courses = new List<addcourse>();
        string strCommandText = "Select statement here"

        SqlCommand cmd = new SqlCommand(strCommandText, conn);
        cmd.Parameters.AddWithValue("@scholarshipid", idcourse);

        conn.Open();

        SqlDataReader myReader = cmd.ExecuteReader();

        while (myReader.Read())
        {
            int sID = Convert.ToInt32(myReader["scholarshipid"].ToString());

            string course = myReader["course"].ToString();

            courses.Add(new addcourse(sID,course));
        }

        myReader.Close();

        return courses;
}

---

为此，我删除了一些字段，以免混淆您创建for循环，然后将其添加到正在使用的变量中。您应该从getCourseDetail和displayCourseInfo返回一个列表，如果addCourse具有Course属性，则可以执行此操作：

lbCourse.Text = string.Join(", ",  courses.Select(x => x.Course));

如果属性名称不同，则将x.Course更改为该名称

所以在你的读者中，你会这样做

    var courses = new List<addcourse>();
    while (myReader.Read())
    {
        int sID = Convert.ToInt32(myReader["courseID"].ToString());

        string course = myReader["course"].ToString();


        courses.Add( new addcourse(sID, course)) ;
   } 
   return courses;

所以，您应该修复这个问题，并确保获得所需的列，因为现在它只获取课程列，并且有语法错误。使用ManagementStudio直接对数据库运行查询。一旦你的查询工作，复制粘贴它，并用一个参数替换where部分，就像你现在拥有的那样

编辑

看来你还坚持着这一点，所以我会给你一个更详细的答案；然而，您应该真正学习一些基本的编程概念。不管怎样，这是：

您的代码隐藏：

protected void btnShowDetails_Click(object sender, EventArgs e)
{
    string Selectedid = GVFBAcc.SelectedRow.Cells[1].Text;//get user id
    int selectedIdtoPass = Convert.ToInt32(Selectedid);

    courseBLL getRecord = new courseBLL();
    addcourse courseRetrieve = new addcourse();
    courseRetrieve = getRecord.getCourseDetail(selectedIdtoPass);

    lbCourse.Text = courseRetrieve.course1 + "," + courseRetrieve.course1;
}

protected void btnShowDetails_Click(object sender, EventArgs e)
{
    string Selectedid = GVFBAcc.SelectedRow.Cells[1].Text;//get user id
    // Make sure this is the scholarshipid or the whole thing will
    // not work.
    int selectedIdtoPass = Convert.ToInt32(Selectedid);

    courseBLL courseRetriever = new courseBLL();

    // Remember you will get a list here
    List<addcourse> courses = courseRetriever.getCourseDetail(selectedIdtoPass);

    // This will take the list and separate the course property with a comma and space
    var courseNames = string.Join(", ", courses);

    // Now assign it to the text property
    lbCourse.Text = courseNames;
}

您的BLL：

// See here you are retuning a list
// But you need to pass the scholarshipid so you can get the courses for that scholarshipid
public List<addcourse> GerCourses(int scholarshipId)
{
        courseDAL courseRetriever = new courseDAL();

        // Get the list
        List<addcourse> courses = courseRetriever.GetCourses(scholarshipId);
        return courses;
}

您的DAL：

// See here you are retuning a list
// But you need to pass the scholarshipid so you can get the courses for that scholarshipid
public List<addcourse> GetCourses(int scholarshipId)
{
        // Make sure your query is correct, see you have spelling mistakes
        // it should be scholarshipid not schokarshipid. it has to match the column in your database
        // Make sure your table is called course and it has 3 columns: 1. courseid 2. course
        // 3. scholarshipid or this query will not work
        string strCommandText = "Select courseid, course from course where scholarshipid = @scholarshipId";

        SqlCommand cmd = new SqlCommand(strCommandText, conn);
        cmd.Parameters.AddWithValue("@scholarshipid", scholarshipId);

        conn.Open();

        SqlDataReader myReader = cmd.ExecuteReader();

        // create a list so we can hold all the courses
        List<addcourse> userObjs = new List<addcourse>();

        // This will read one row at a time so keep reading until there are no more records
        while (myReader.Read())
        {
            int sID = Convert.ToInt32(myReader["courseid"].ToString());

            string course = myReader["course"].ToString();

            addcourse userObj = new addcourse(sID, course);

            // add it to the list
            userObjs.Add(userObj);
        }

        myReader.Close();

        // return the list
        return userObjs;
}

还有一些提示：

给你的方法起个更有意义的名字。看看我给他们的名字，现在它读起来像英语，而且很容易理解。 你的课程应该叫做课程。addcourse听起来像是一个ActionAddCourse，如果您正在添加课程，这可能是一个很好的方法名称。类名称和方法名称也使用Pascal表示法。参数、参数和局部变量使用驼峰式大小写。 了解如何使用Visual Studio调试器。在VisualStudio上观看一些YouTube视频。

---

GetCourseDetail中发生了什么？你当前的lbCourse输出是什么？Text？？我已经编辑了代码，请看@un luckycurrent output是：Math，mathsdo你有什么例子吗？我使用vb.net，如果你想检查你的查询，你可以转换它，你似乎正在调用courseid，id是：1 course=maths，尝试删除where条件，它将输出数据库中的所有数据。您能建议我如何执行列表吗？与您现在调用它的方式相同。只需按照我的代码和返回列表中的那些方法我得到了一个错误，说它不能隐式转换从列表到BLL近返回课程我已经添加了编辑代码以上，请帮助采取我的坏。我还有一些其他字段要检索，但我没有相应地删除它。基本上，courseID是另一个表的外键。因此，当courseID=1时，它将在另一个表中显示所有这些课程和其他详细信息