ASP.NET MessageBox在上下文中不存在

Question

I have created a connection class in asp.net to save values in list i have written following code but it is generating error that MessageBox doesn't exist. I google this and have found few answers but these are also not working here my code is:

 public static class Connection
    {
        public static ArrayList GetCoffeeByType(string coffeetype)
        {
            ArrayList list = new ArrayList();
            try
            {
                mydbEntities db = new mydbEntities();
                var query = from p in db.tableabc select p;
                list = query.ToList();

            }
            catch (Exception ex)
            {
               MessageBox.Show(exceptionObj.Message.ToString());

            }
            return list;
        }
}

I tried this System.Web.UI.ScriptManager.RegisterStartupScript(this, typeof(Page), "alert", "alert('" + Message + "')", true); -- But it is also showing error at this and Message -- how can i show this MessageBox?

Answer 1

You won't be able to invoke MessageBox.Show in an ASP.NET application. Try this instead:

catch (Exception ex)
{
    var script = "alert(" + System.Web.HttpUtility.JavaScriptStringEncode(ex.Message, true) + ")";
    System.Web.UI.ScriptManager.RegisterStartupScript(this, typeof(Page), "alert", script, true);
}

Note that you need to get the Message property on the caught exception, ex , and you should use JavaScriptStringEncode to safely escape the alert message.

Answer 2

This is a static class called Alert with one public method called Show. The implementation is as simple as can be. Just put the .cs file in the App_Code folder on your website and you instantly have access to the method from all pages and user controls.

using System.Web;
using System.Text;
using System.Web.UI;

/// <summary>
/// A JavaScript alert
/// </summary>
publicstaticclass Alert
{

/// <summary>
/// Shows a client-side JavaScript alert in the browser.
/// </summary>
/// <param name="message">The message to appear in the alert.</param>
publicstaticvoid Show(string message)
{
   // Cleans the message to allow single quotation marks
   string cleanMessage = message.Replace("'", "\\'");
   string script ="<script type=\"text/javascript\">alert('"+ cleanMessage +"');</script>";

   // Gets the executing web page
   Page page = HttpContext.Current.CurrentHandler as Page;

   // Checks if the handler is a Page and that the script isn't allready on the Page
   if (page !=null && !page.ClientScript.IsClientScriptBlockRegistered("alert"))
   {
      page.ClientScript.RegisterClientScriptBlock(typeof(Alert), "alert", script);
   }
}    
}

Demonstration

That class enables you to add a JavaScript alert to any page at any time. Here is an example of a Button.Click event handler that uses the method for displaying status messages.

void btnSave_Click(object sender, EventArgs e)
{
   try
   {

      Alert.Show("Your Message");
   }
   catch (Exeception ex )
   {
      Alert.Show(ex.Message);
   }
}

In your Case :

public static class Connection
    {
        public static ArrayList GetCoffeeByType(string coffeetype)
        {
            ArrayList list = new ArrayList();
            try
            {
                mydbEntities db = new mydbEntities();
                var query = from p in db.tableabc select p;
                list = query.ToList();

            }
            catch (Exception ex)
            {
               Alert.Show(ex.Message);

            }
            return list;
        }
}