C# 如何返回foreach循环中的所有数据

我在.NETCore中有一个生成ID卡的项目。当我为一个学生打印身份证时，一切正常，但我在打印多张身份证时遇到问题

我的控制器中的get方法如下：

[HttpGet]
[AllowAnonymous]
public IActionResult BulkCard()
{
        //values = ViewBag.Cards;
        var values = (object[])TempData["students"]; //This retrieves all students that has been selected to print their ID Card
        ViewBag.Cards = values.ToArray();
        var designtemplate = _context.Settings.First();

        if (designtemplate.CardTemplate == 1)
        {
            ViewBag.Template = "1";
        }
        else if (designtemplate.CardTemplate == 2)
        {
            ViewBag.Template = "2";
            ViewBag.TemplateView = "This is template 2";
        }
        else if (designtemplate.CardTemplate == 3)
        {
            ViewBag.Template = "3";
            ViewBag.TemplateView = "This is template 3";
        }
        else
        {
            return RedirectToAction("CardSettings", "Settings");
        }

        var model = new ModelClasses();

        foreach (var item in values)
        {
            model.Students = _context.Students.ToList();
            model.Student = _context.Students.Include(c => c.Department).Include(c => c.Department.Faculty).Include(c => c.ProgramType).Include(c => c.ClassLevels).Include(c => c.Session).ToList().FirstOrDefault(c => c.Id == Convert.ToInt32(item));
            ViewBag.Students = _context.Students.Include(c => c.Department).Include(c => c.Department.Faculty).Include(c => c.ProgramType).Include(c => c.ClassLevels).Include(c => c.Session).ToList().Where(c => c.Id == Convert.ToInt32(item)).ToList();
            var surname = model.Student.Surname;
            var firstname = model.Student.FirstName;
            var middleName = model.Student.MiddleName[0];
            var fullname = surname + " " + firstname + " " + middleName + ".";

            ViewBag.FullName = fullname;
            ViewBag.MatricNumber = model.Student.MatricNumber;
            ViewBag.Department = model.Student.Department;
            ViewBag.Faculty = model.Student.Faculty;
            ViewBag.Passport = "/Uploads" + "/Passport/" + model.Student.Passport;
            ViewBag.Signature = "/Uploads" + "/Signature/" + model.Student.Signature;

            var qrdata = model.Student.QRCodeData.ToString().Replace("/", "");

            using (MemoryStream ms = new MemoryStream())
            {
                QRCodeGenerator qrGenerator = new QRCodeGenerator();
                QRCodeData qrCodeData = qrGenerator.CreateQrCode(qrdata, QRCodeGenerator.ECCLevel.Q);
                QRCode qrCode = new QRCode(qrCodeData);

                using (Bitmap bitMap = qrCode.GetGraphic(20))
                {
                    bitMap.Save(ms, ImageFormat.Png);
                    ViewBag.QRCodeImage = "data:image/png;base64," + Convert.ToBase64String(ms.ToArray());
                }
            }
        }

        return View(model);
 }

我的看法如下：

@foreach (var item in ViewBag.Students)
{
    @if (ViewBag.Template == "1")
    {
        <table>
            <tr>
                <td>
                    BULK CARD PRINTING
                    <img src="@ViewBag.QRCodeImage" class="qrcode">
                </td>
            </tr>
        </table>
        @*<table>
            <tr>
                <td>
                    <div class="wrapper">
                        <div class="container">
                            <div style="position: absolute;color: lightgray;opacity: 0.05;font-size: 3em;width: 50%;top: 25%; left: 80px;text-align: center;z-index: 0;background-attachment: fixed;"><img src="~/img/fedpolel-Logo.png" width="150" /></div>
                            <img src="~/Uploads/Passport//@item.Passport" alt="" class="profile-img">

                            <img src="~/img/fedpolel-Logo.png" class="logo" />

                            <img src="@ViewBag.QRCodeImage" class="qrcode">

                            <div class="content">
                                <table>
                                    <tr>
                                        <td>
                                            <div class="title">
                                                <h4>THE FEDERAL POLYTECHNIC</h4>
                                                <span>ILE OLUJI, ONDO STATE.</span>

                                            </div>

                                            <div class="sub-content">
                                                <center>
                                                    <h1>@item.FullName</h1>
                                                </center>
                                                <p>@item.MatricNumber</p>
                                            </div>
                                            <div class="vr"></div>
                                            <div class="vr-right"></div>
                                            <div class="data">
                                                <div class="inner-data">
                                                    <span>Gender</span>
                                                    <p>@item.Gender<p />
                                                    <br>
                                                    <span>Session</span>
                                                    <p class="session">@item.Session.SessionName</p>
                                                </div>
                                                <div class="inner-data2">
                                                    <span>Level</span>
                                                    <p>@item.ClassLevels.ClassLevel</p>
                                                    <span>Department</span>
                                                    <p>@item.Department.DepartmentName</p>
                                                    <span>Faculty</span>
                                                    <p>@item.Department.Faculty.FacultyName</p>
                                                </div>
                                                <div class="inner-data3">
                                                    <div class="hr"></div>
                                                    <p><img src="@ViewBag.Signature" width="50" /></p>
                                                    <div class="paragra">Signature</div>
                                                </div>
                                            </div>
                                        </td>
                                    </tr>
                                </table>


                            </div>
                        </div>
                    </div>
                </td>
            </tr>
        </table>*@
    }
    else if (ViewBag.Template == "2")
    {
        @ViewBag.TemplateView
    }
    else if (ViewBag.Teplate == "3")
    {
        @ViewBag.TemplateView
    }
    else
    {
        @ViewBag.NoTemplateView
    }
}

@foreach（ViewBag.Students中的变量项）
{
@如果（ViewBag.Template==“1”）
{
批量制卡
@*
联邦理工学院
奥卢吉岛，昂多州。
@item.FullName
@item.MatricNumber

性别
@项目.性别



一场
@item.session.SessionName
水平仪
@item.ClassLevels.ClassLevel

部门
@item.Department.Department名称

官能
@item.Department.Faculty.FacultyName


签名
*@
}
else if（ViewBag.Template==“2”）
{
@ViewBag.TemplateView
}
否则如果（ViewBag.Teplate==“3”）
{
@ViewBag.TemplateView
}
其他的
{
@ViewBag.NoTemplateView
}
}

此代码仅返回最后一个学生的数据

---

我的挑战：如果我预选了5名学生，我想返回这5名学生的数据。请问，我该如何实现这一点？

之所以发生这种情况，是因为您总是在每个循环迭代中将

ViewBag.Students

设置为新列表（它只包含一条记录，因为您是按Id筛选的）

初始化

ViewBag.Students

循环外部（例如

ViewBag.Students=new List

，循环内部只需从数据库中添加已读学生（

model.student

）

e、 g:

另外，尝试在for循环之外填充

model.Students

，因为当前您在每次迭代（

model.Students=\u context.Students.ToList（）

）时都会对数据库进行不必要的访问。在每次for循环迭代中，您都会将完整的Students读取到model属性，这是多余的。一次就足够了

---

我还认为您不需要将ViewBag的属性设置为模型的属性。只需传递一个模型（可能添加一些所需的属性）查看并读取模型中的数据。

好的，谢谢。我需要更改视图中的任何内容吗？如果您使用模型而不是ViewBag，您可能需要更改每个循环以读取模型中的数据，而不是ViewBag。此外，如果我的答案帮助您解决了问题，请将其标记为已接受的答案。但是，尚未实现这一点，您该怎么做我开始动态生成二维码图像？您可以向模型添加属性以包含二维码，就像现在使用ViewBag一样。然后从模型而不是ViewBag读取其值。我不想将其保存到数据库中

ViewBag.Students.Add(model.Student);