c# - ViewBag 空空如也

Question

我有一个在数据库中注册聊天的表单，一切正常，问题是 ViewBag，因为这会将消息带到 View 中的 Javascript，以便它可以进行验证。当用户注册时，应该会出现一条成功消息，但在 ViewBag 中它显示为错误，如果显示了用户的数据，则在数据库中，所以唯一的问题是 ViewBag。

此外，当我再次重新运行时，带有成功消息的模态显示得很好。

Controller

//Charlas
    public ActionResult CrearCharla()
    {
        List<ClsSede> listaSede = new List<ClsSede>();

        ClsSede Sede1 = new ClsSede();
        Sede1.sede_Text = "LIMA - SAN BORJA";
        Sede1.sede_Value = "LIMA - SAN BORJA";

        ClsSede Sede2 = new ClsSede();
        Sede2.sede_Text = "LIMA - LOS OLIVOS";
        Sede2.sede_Value = "LIMA - LOS OLIVOS";

        ClsSede Sede3 = new ClsSede();
        Sede3.sede_Text = "LIMA - CHORRILLOS";
        Sede3.sede_Value = "LIMA - CHORRILLOS";

        listaSede.Add(Sede1);
        listaSede.Add(Sede2);
        listaSede.Add(Sede3);

        ViewBag.Sedes = new SelectList(listaSede, "sede_Text", "sede_Value");

        return View(new ClsCharla());
    }

    [HttpPost]
    public ActionResult CrearCharla(ClsCharla charla)
    {

        List<ClsSede> listaSede = new List<ClsSede>();

        ClsSede Sede1 = new ClsSede();
        Sede1.sede_Text = "LIMA - SAN BORJA";
        Sede1.sede_Value = "LIMA - SAN BORJA";

        ClsSede Sede2 = new ClsSede();
        Sede2.sede_Text = "LIMA - LOS OLIVOS";
        Sede2.sede_Value = "LIMA - LOS OLIVOS";

        ClsSede Sede3 = new ClsSede();
        Sede3.sede_Text = "LIMA - CHORRILLOS";
        Sede3.sede_Value = "LIMA - CHORRILLOS";

        listaSede.Add(Sede1);
        listaSede.Add(Sede2);
        listaSede.Add(Sede3);

        ViewBag.Sedes = new SelectList(listaSede, "sede_Text", "sede_Value", charla.sede_Charla);

        //-----

        string message = "";

        try
        {
            ClsConexion con = new ClsConexion();
            var Cnx = con.Conexion();

            OracleCommand cmd = new OracleCommand("SIMEXA_SP_REGISTER_CHAT", Cnx);
            cmd.CommandType = CommandType.StoredProcedure;
            cmd.Parameters.Add(new OracleParameter("param_titulo", OracleDbType.Varchar2)).Value = charla.titulo_Charla.Trim();
            cmd.Parameters.Add(new OracleParameter("param_descrip", OracleDbType.Varchar2)).Value = charla.descrip_Charla.Trim();
            cmd.Parameters.Add(new OracleParameter("param_fecha", OracleDbType.Varchar2)).Value = charla.fecha_Charla;
            cmd.Parameters.Add(new OracleParameter("param_hora", OracleDbType.Varchar2)).Value = charla.hora_Charla;
            cmd.Parameters.Add(new OracleParameter("param_lugar", OracleDbType.Varchar2)).Value = charla.lugar_Charla.Trim();
            cmd.Parameters.Add(new OracleParameter("param_sede", OracleDbType.Varchar2)).Value = charla.sede_Charla;
            cmd.Parameters.Add(new OracleParameter("param_requisito", OracleDbType.Varchar2)).Value = charla.requisito_Charla.Trim();
            Cnx.Open();

            OracleTransaction tx = Cnx.BeginTransaction();
            cmd.ExecuteNonQuery();
            tx.Commit();

            Cnx.Close();
            cmd.Dispose();
            Cnx.Dispose();

            message = "success";

        }
        catch
        {
            message = "error";
        }
        finally
        {
            ViewBag.message = message;
        }

        return RedirectToAction("MostraCharlas");

    }

查看

    @model wsCharlas.Models.ClsCharla

@{
    ViewBag.Title = "Create a Chat";
    Layout = "~/Views/Shared/_Layout.cshtml";
}

<h2>Create a Chat:</h2>

@using (Html.BeginForm())
{
    @Html.AntiForgeryToken()

    <h4>Here you can place all the respective data of the chat you want to create.</h4>
    <hr />

    @Html.ValidationSummary(true, "", new { @class = "text-danger" })

    <!--    <div class="form-horizontal"> -->
    <div class="form-group">
        @Html.HiddenFor(model => model.ID_Charla, htmlAttributes: new { @class = "control-label" })
        <div>
            @Html.HiddenFor(model => model.ID_Charla, new { htmlAttributes = new { @class = "form-control" } })
            @Html.ValidationMessageFor(model => model.ID_Charla, "", new { @class = "text-danger" })
        </div>
    </div>

    <div class="form-group">
        @Html.LabelFor(model => model.titulo_Charla, htmlAttributes: new { @class = "control-label" })
        <div>
            @Html.EditorFor(model => model.titulo_Charla, new { htmlAttributes = new { @class = "form-control", maxlength = "40" } })
            @Html.ValidationMessageFor(model => model.titulo_Charla, "", new { @class = "text-danger" })
        </div>
    </div>

    <div class="form-group">
        @Html.LabelFor(model => model.descrip_Charla, htmlAttributes: new { @class = "control-label" })
        <div>
            @Html.TextAreaFor(model => model.descrip_Charla, new { @id = "textArea", @class = "form-control", maxlength = "530" })
            @Html.ValidationMessageFor(model => model.descrip_Charla, "", new { @class = "text-danger" })
        </div>
    </div>

    <div class="form-group">
        @Html.LabelFor(model => model.fecha_Charla, htmlAttributes: new { @class = "control-label" })
        <div>
            @Html.EditorFor(model => model.fecha_Charla, new { htmlAttributes = new { @class = "form-control" } })
            @Html.ValidationMessageFor(model => model.fecha_Charla, "", new { @class = "text-danger" })
        </div>
    </div>

    <div class="form-group">
        @Html.LabelFor(model => model.hora_Charla, htmlAttributes: new { @class = "control-label" })
        <div>
            @Html.EditorFor(model => model.hora_Charla, new { htmlAttributes = new { @class = "form-control" } })
            @Html.ValidationMessageFor(model => model.hora_Charla, "", new { @class = "text-danger" })
        </div>
    </div>

    <div class="form-group">
        @Html.LabelFor(model => model.lugar_Charla, htmlAttributes: new { @class = "control-label" })
        <div>
            @Html.EditorFor(model => model.lugar_Charla, new { htmlAttributes = new { @class = "form-control", maxlength = "100" } })
            @Html.ValidationMessageFor(model => model.lugar_Charla, "", new { @class = "text-danger" })
        </div>
    </div>

    <div class="form-group">
        @Html.LabelFor(model => model.sede_Charla, htmlAttributes: new { @class = "control-label" })
        <div>
            @Html.DropDownListFor(model => model.sede_Charla, (SelectList)ViewBag.Sedes, "Select a Headquarters", new { @class = "form-control" })
            @Html.ValidationMessageFor(model => model.sede_Charla, "", new { @class = "text-danger" })
        </div>
    </div>

    <div class="form-group">
        @Html.LabelFor(model => model.requisito_Charla, htmlAttributes: new { @class = "control-label" })
        <div>
            @Html.EditorFor(model => model.requisito_Charla, new { htmlAttributes = new { @class = "form-control", maxlength = "100" } })
            @Html.ValidationMessageFor(model => model.requisito_Charla, "", new { @class = "text-danger" })
        </div>
    </div>

    <div class="form-group">
        <div class="col-md-offset-2">
            <input type="submit" value="Create a Chat" id="id_charla"  class="btn btn-success" />
        </div>
    </div>
    <!--</div> -->
}

<div>
    @Html.ActionLink("Return", "MostraCharlas", null, new { @class = "btn btn-primary" })
</div>

@section Scripts {
    @Scripts.Render("~/bundles/jqueryval")
}

<style>
    #textArea{
        min-height: 62px;
        max-height: 135px;
    }
</style>

<script>

    var msg = '@ViewBag.message'

    $("#id_charla").on("click", function () {
        if (msg == 'success') {
            Swal.fire(
                        msg,
                        'A new chat was added!',
                        'success'
                     )
        } else {
            Swal.fire(
                        msg,
                        'Could not register your new chat, be sure to complete the entire form, if the problem continues to communicate with the computer area!',
                        'error'
                     )
        }   
    });

</script>

Answer 1

为了回答您的问题，我首先要说的是，在您的案例中为 ViewBag 获取 null 实际上是正确的，因为您使用了 RedirectToAction 这将使所有 ViewBag数据

ViewBag 的生命周期是当前请求，这意味着一旦您尝试离开当前请求，它就会变为空。所以你需要在你自己的情况下使用 TempData。

TempData 是一种按照 session 存储方式存储的数据。它的生命周期持续在两个请求之间。它有助于将数据从一个 Controller 传输到另一个 Controller 或从一个 Action 传输到另一个 Action 。您使用 TempData 的方式与使用 View data 或 ViewBag 的方式略有不同。

所以我给你两个选择。

第一

使用 TempData 和 ViewBag

在 Post 操作中将 finally 行更改为

finally
{
    TempData["message"] = message;
}

然后在你重定向到的Get action中，因为你使用了RedirectToAction，获取TempData并将它传递给view bag

var message = TempData ["message"];
If(message != null)
    ViewBag.message = message;

注意 需要 if 语句来处理初始 get 请求，即在未设置 TempData 时不设置 ViewBag 的值

第二

仅使用 TempData

finally
{
    TempData["message"] = message;
}

无论您决定使用哪个，访问方式都与您分配它的方式相同，

TempData["message"] //for TempData
ViewBag.message //for ViewBag