“System.Data.DataRowView”在下拉列表中

Question

我无法将数据绑定到下拉列表..任何人都可以解释我为什么吗？ 错误是：“System.Data.DataRowView”不包含名称为“_DeptID”的属性。 我的代码是：

public class ClassDataManagement
{
    public DataTable BindDropDownList(string Sql, DropDownList DropDownList)
    {
        SqlConnection cn = new SqlConnection(@"Data Source=ABID-PC;Initial Catalog=_uniManagement;Integrated Security=True");
        SqlCommand cmd = new SqlCommand(Sql, cn);
        SqlDataAdapter da = new SqlDataAdapter(cmd);
        DataTable dt = new DataTable();
        da.Fill(dt);
        if (dt.Rows.Count == 0)
        {

        }
        else
        {
            DropDownList.DataTextField = "Name";
            DropDownList.DataValueField = "_DeptID";
            DropDownList.DataSource = dt.DefaultView;
            DropDownList.DataBind();
        }
        return dt;
    }

}
protected void Page_Load(object sender, EventArgs e)
{
    ClassDataManagement dm = new ClassDataManagement();
    dm.BindDropDownList("select _Program.Name from _program,_Department where _program._Deptid = _department._DeptId", DropDownListProgram);
}

Answer 1

您没有在 SQL 语句中返回名为 _Deptid 的列。

您的 SQL 语句应为：

select _program.Name, _program._Deptid 
  from _program,_Department 
 where _program._Deptid = _Department._DeptId

正如 Stackoverflow 用户所提到的，通过使用 using 语句，这将自动处理您的对象。另一件事，你正在做：

if (dt.Rows.Count == 0)

但里面没有代码。无论您是否在实际代码中执行此操作，但如果您打算将其留空，建议执行以下操作：

if (dt.Rows.Count > 0)
{
    DropDownList.DataTextField = "Name";    
    DropDownList.DataValueField = "_DeptID";    
    DropDownList.DataSource = dt.DefaultView;    
    DropDownList.DataBind();
}

Answer 2

1. select 语句中缺少 _Dept 列

2. 缺少对象的处置。所以你可以通过两种方式执行它

   (a) 手动处置

   (b) 使用语句

---

public class ClassDataManagement
{
    public DataTable BindDropDownList(string Sql, DropDownList DropDownList)
    {
        using (SqlConnection cn = new SqlConnection(@"Data Source=ABID-PC;Initial Catalog=_uniManagement;Integrated Security=True"))
        {
            using (SqlCommand cmd = new SqlCommand(Sql, cn))
            {
                using(SqlDataAdapter da = new SqlDataAdapter(cmd))
                {
                    using (DataTable dt = new DataTable())
                    {
                        da.Fill(dt);
                        DropDownList.DataTextField = "Name";
                        DropDownList.DataValueField = "_Deptid";
                        DropDownList.DataSource = dt.DefaultView;
                        DropDownList.DataBind();
                        return dt;
                    }
                }
            }
        }
    }

}
protected void Page_Load(object sender, EventArgs e)
{
    ClassDataManagement dm = new ClassDataManagement();
    dm.BindDropDownList("select _Program.Name, _program._Deptid from _program,_Department "
        + "where _program._Deptid = _department._DeptId", DropDownListProgram);

}

EDIT - 1

以及为SqlDataAdapter添加Using语句

Answer 3

将 SQL 更改为：

select _Program.Name, _Program._DeptId from _program,_Department where _program._Deptid = _department._DeptId

Answer 4

尝试将您的代码修改为此，您缺少 _DeptID

   protected void Page_Load(object sender, EventArgs e)
    {
        ClassDataManagement dm = new ClassDataManagement();
        dm.BindDropDownList("select _Program.Name,_DeptID from _program,_Department where _program._Deptid = _department._DeptId", DropDownListProgram);

    }