将 C# 转换为 VB.NET：具有返回类型的委托类型的事件

Question

我正在尝试在 ASP.NET 中处理多个客户端回调，我正在关注这个article

我已将 C# 代码转换为我的环境 VB.NET/ASP.NET。

使用的命名空间是 SmartSoft.Web.UI.WebControls

在名为 ClientCallback 的类中，我有这段代码

Public Delegate Function OnRaiseCallbackEvent(ByVal eventArgument As String) As String

Public Event Raise As OnRaiseCallbackEvent

编译器用以下错误消息标记事件声明：

不能使用具有返回类型的委托类型来声明事件。

我尝试遵循解决方案here 但如果声明

Public Raise As OnRaiseCallbackEvent

我在另一个名为 SampleCompositeControl

的类中收到另一个错误

我在哪里

Private button1 As Button
Private button1Callback As ClientCallback

Protected Overrides Sub OnPreRender(ByVal e As System.EventArgs)
   ......
End Sub

Protected Overrides Sub CreateChildControls()
    button1 = New Button With {.ID = "Button1",.Text = "Button 1",
            .OnClientClick = "button1Clicked('', '', callbackComplete);return false;"}

        Controls.Add(button1)
        button1Callback = New ClientCallback With {
            .ID = "button1Callback"}

        button1Callback.Raise += AddressOf button1Callback_Raise
        ..........
    End Sub

    Protected Overrides Sub RenderContents(ByVal writer As HtmlTextWriter)
       ........
    End Sub

    Private Function button1Callback_Raise(ByVal eventArgument As String) As String
        Return "Button 1 callback processed."
    End Function

    Private Shared Function GetResource(ByVal resourceName As String) As String
       ..........
    End Function

    Private Function GetCallbackReference(ByVal control As Control) As String
        Return Page.ClientScript.GetCallbackEventReference(control, "arg", "callback", "context")
    End Function

编译器标记 button1Callback.Raise += AddressOf button1Callback_Raise

带有此错误消息：

'+' 运算符没有为类型“SmartSoft.Web.UI.WebControls.SmartSoft.Web.UI.WebControls.ClientCallback.OnRaiseCallbackEvent”和“Void”定义。

如何在不丢失功能的情况下正确地将代码从 C# 转换为 VB.NET？

Answer 1

VB.NET 使用AddHandler 进行事件注册，而C# 使用+= 语法。

试试AddHandler button1Callback.Raise, AddressOf button1Callback_Raise

Answer 2

这样解决：

遵循 djv 的建议（在 VB.NET 中不可能让事件返回像 C# 中的值）

我在 C# 中构建了一个 WebControl，向 probject 添加了控件 并将此标签放入 ASPX Page

<%@ Register Assembly="SmartOBJ.Web.UI.WebControls" Namespace="SmartOBJ.Web.UI.WebControls" TagPrefix="SmartOBJ" %>

<SmartOBJ:SampleControl ID="SampleControl1" runat="server" />

这是 ASPX 中的点击调用

..... other javascript code
switch (Type) {
    case 'E':
        delRECORD(ID_RECORDD.toString()+';E', '', callbackComplete); return false;break;
    case 'SC':
        delRECORD(ID_RECORDD.toString() + ';SC', '', callbackComplete); return false;break;
    case 'SS':
        mess = 'xxxx';break;}
........

这个 c# 文件：

using System.IO;
using System.Reflection;
using System.Web.UI;

using System.Web.UI.WebControls;
using System.Text.RegularExpressions;

[assembly: TagPrefix("SmartOBJ.Web.UI.WebControls", "SmartOBJ")]
namespace SmartOBJ.Web.UI.WebControls
{
    [ToolboxData("<{0}:SampleControl runat=server></{0}:SampleControl>")]
    public class SampleControl : CompositeControl
    {
        #region members
        private Button button1;
        private ClientCallback delRECORD;
        #endregion

        protected override void OnPreRender(System.EventArgs e)
        {
            base.OnPreRender(e);

            // Register client side script for the callbacks
            string clientScript = GetResource("SmartOBJ.Web.UI.WebControls.Resources.SampleControlClientScript.js");
            clientScript = clientScript.Replace("{button1_callback_reference}", GetCallbackReference(button1Callback));
            clientScript = clientScript.Replace("{delRECORD_callback_reference}", GetCallbackReference(delRECORD));
            Page.ClientScript.RegisterClientScriptBlock(GetType(), "client_script", clientScript, true);
        }

        protected override void CreateChildControls()
        {
            // Create buttons
            button1 = new Button
                          {
                              ID = "Button1",
                              Text = "Button 1",
                              Visible = false,
                              OnClientClick = "button1Clicked(ID_RECORD, '', callbackComplete);return false;"

                          };
            Controls.Add(button1);


            // Create callback controls
            delRECORD = new ClientCallback { ID = "delRECORD" };
            delRECORD.Raise += delRECORD_Raise;
            Controls.Add(delRECORD);


        }

        protected override void RenderContents(HtmlTextWriter writer)
        {
            // Render buttons
            button1.RenderControl(writer);

            // Render result div
            writer.AddAttribute(HtmlTextWriterAttribute.Id, "result");
            writer.RenderBeginTag(HtmlTextWriterTag.Div);
            writer.RenderEndTag();

            // Render callback controls
            delRECORD.RenderControl(writer);
        }

        /// Handles client callback events for delRECORD.
        /// <param name="eventArgument">
        private string delRECORD_Raise(string eventArgument)
        {
            ToolsDB mytool=new ToolsDB();
            bool verify=false;
            string msg="";
            string msg2 = "";

            string[] parameters = Regex.Split(eventArgument, ";"); 

            if  (parameters[1] == "E")
                {
                    msg = "msg1";
                    msg2= " msg2"; 
                    verify=mytool.delRECORD(parameters[0],parameters[1]); // This part execute other code to manage DB and is defined in another class
                }

            if (parameters[1] == "SC")
            {
                msg = " msg1";
                msg2 = " msg2";
                verify = mytool.delRECORD(parameters[0], parameters[1]);
            }


            if (verify == true) 
                {return "ALLISOK;" + parameters[0] +";Record with ID " + parameters[0] + msg;}
            else
                { return "NOTOK;" + parameters[0] + ";Record with ID " + parameters[0] + msg2; }        
        }

        private string button1Callback_Raise(string eventArgument)
        {
            return eventArgument.ToString() + "_" + "Button 1 callback processed." ;
        }


        /// Helper to load embedded resource as a string.
        private static string GetResource(string resourceName)
        {
            Assembly assembly = Assembly.GetExecutingAssembly();
            string result = string.Empty;
            Stream resourceStream = assembly.GetManifestResourceStream(resourceName);
            if (resourceStream != null)
            {
                using (TextReader textReader = new StreamReader(resourceStream))
                {
                    result = textReader.ReadToEnd();
                }
            }
            return result;
        }

        private string GetCallbackReference(Control control)
        {
            return Page.ClientScript.GetCallbackEventReference(control, "arg", "callback", "context");
        }
    }
}

js中这个资源文件包含

function button1Clicked(arg, context, callback) {
    {button1_callback_reference};
}


function delRECORD(arg, context, callback) {
    {delRECORD_callback_reference};
}

function callbackComplete(result, context) {
    var parameters = result.split(";");
    if (parameters[0] == 'ALLISOK')
        {
        $table.bootstrapTable('remove', {
            field: 'id',
            values: [IDRow]
        });
        alert(parameters[2]);
        $('#deletemovedir').modal('toggle');
    }
    else
        {
        alert(parameters[2]);
        }
}