Develop Reference

ADO.NET - Resilient Connection to Oracle Database using OracleClient

We have a legacy C# Windows Service application (.Net Framework 4.8) that performs some statistical analysis which usually takes hours to complete as the underlying database has millions of rows of historical data.
It works fine if there is no underlying network interruption. However, we recently started using a database which is only accessible over the VPN. Now if there is any VPN connection issue, the analysis stops.
Is there any way to recover from these transient faults silently and gracefully and continue the work?
For the SqlClient I have found a sample code at https://learn.microsoft.com/en-us/sql/connect/ado-net/step-4-connect-resiliently-sql-ado-net?view=sql-server-ver15
The sample code from the link is shown below (just in case if the link dies).
using System; // C#
using CG = System.Collections.Generic;
using QC = Microsoft.Data.SqlClient;
using TD = System.Threading;
namespace RetryAdo2
{
public class Program
{
static public int Main(string[] args)
{
bool succeeded = false;
int totalNumberOfTimesToTry = 4;
int retryIntervalSeconds = 10;
for (int tries = 1;
tries <= totalNumberOfTimesToTry;
tries++)
{
try
{
if (tries > 1)
{
Console.WriteLine
("Transient error encountered. Will begin attempt number {0} of {1} max...",
tries, totalNumberOfTimesToTry
);
TD.Thread.Sleep(1000 * retryIntervalSeconds);
retryIntervalSeconds = Convert.ToInt32
(retryIntervalSeconds * 1.5);
}
AccessDatabase();
succeeded = true;
break;
}
catch (QC.SqlException sqlExc)
{
if (TransientErrorNumbers.Contains
(sqlExc.Number) == true)
{
Console.WriteLine("{0}: transient occurred.", sqlExc.Number);
continue;
}
else
{
Console.WriteLine(sqlExc);
succeeded = false;
break;
}
}
catch (TestSqlException sqlExc)
{
if (TransientErrorNumbers.Contains
(sqlExc.Number) == true)
{
Console.WriteLine("{0}: transient occurred. (TESTING.)", sqlExc.Number);
continue;
}
else
{
Console.WriteLine(sqlExc);
succeeded = false;
break;
}
}
catch (Exception Exc)
{
Console.WriteLine(Exc);
succeeded = false;
break;
}
}
if (succeeded == true)
{
return 0;
}
else
{
Console.WriteLine("ERROR: Unable to access the database!");
return 1;
}
}
/// <summary>
/// Connects to the database, reads,
/// prints results to the console.
/// </summary>
static public void AccessDatabase()
{
//throw new TestSqlException(4060); //(7654321); // Uncomment for testing.
using (var sqlConnection = new QC.SqlConnection
(GetSqlConnectionString()))
{
using (var dbCommand = sqlConnection.CreateCommand())
{
dbCommand.CommandText = #"
SELECT TOP 3
ob.name,
CAST(ob.object_id as nvarchar(32)) as [object_id]
FROM sys.objects as ob
WHERE ob.type='IT'
ORDER BY ob.name;";
sqlConnection.Open();
var dataReader = dbCommand.ExecuteReader();
while (dataReader.Read())
{
Console.WriteLine("{0}\t{1}",
dataReader.GetString(0),
dataReader.GetString(1));
}
}
}
}
/// <summary>
/// You must edit the four 'my' string values.
/// </summary>
/// <returns>An ADO.NET connection string.</returns>
static private string GetSqlConnectionString()
{
// Prepare the connection string to Azure SQL Database.
var sqlConnectionSB = new QC.SqlConnectionStringBuilder();
// Change these values to your values.
sqlConnectionSB.DataSource = "tcp:myazuresqldbserver.database.windows.net,1433"; //["Server"]
sqlConnectionSB.InitialCatalog = "MyDatabase"; //["Database"]
sqlConnectionSB.UserID = "MyLogin"; // "#yourservername" as suffix sometimes.
sqlConnectionSB.Password = "MyPassword";
sqlConnectionSB.IntegratedSecurity = false;
// Adjust these values if you like. (ADO.NET 4.5.1 or later.)
sqlConnectionSB.ConnectRetryCount = 3;
sqlConnectionSB.ConnectRetryInterval = 10; // Seconds.
// Leave these values as they are.
sqlConnectionSB.IntegratedSecurity = false;
sqlConnectionSB.Encrypt = true;
sqlConnectionSB.ConnectTimeout = 30;
return sqlConnectionSB.ToString();
}
static public CG.List<int> TransientErrorNumbers =
new CG.List<int> { 4060, 40197, 40501, 40613,
49918, 49919, 49920, 11001 };
}
/// <summary>
/// For testing retry logic, you can have method
/// AccessDatabase start by throwing a new
/// TestSqlException with a Number that does
/// or does not match a transient error number
/// present in TransientErrorNumbers.
/// </summary>
internal class TestSqlException : ApplicationException
{
internal TestSqlException(int testErrorNumber)
{ this.Number = testErrorNumber; }
internal int Number
{ get; set; }
}
}
However, I couldn't find any helpful material for the OracleClient. Any ideas, please?

Read All Value From Cache

i am using .netcore with Microsoft.Extensions.Caching.Distributed , i have a scenario to get all the keys and also i need to flush all the values.
I have searched many articles no one gives the exact idea to get all values or Flush values. IDistributedCache don't have flush the redis cache.
Can anyone help on this.

For my project ,the follow function return all matched keys:
//using StackExchange.Redis;
/// <summary>
/// 搜索所有与<see cref="keyStr"/>相匹配的缓存的key
/// </summary>
/// <param name="keyStr">搜索词,*表示任意字符</param>
/// <param name="dbIndex">redis中查找db</param>
/// <param name="trimRedisInstanceName">是否在查询前及返回前去除<see cref="Extension.RedisInstanceName"/>前缀</param>
/// <returns>redis中的key列表,<see cref="trimRedisInstanceName"/>参数设置是否包括<see cref="Extension.RedisInstanceName"/></returns>
protected async Task<List<string>> FilterByKey(string keyStr, int dbIndex = 0, bool trimRedisInstanceName = true)
{
//创建连接
var conn = await ConnectionMultiplexer.ConnectAsync(_configuration.GetSection("Cache")["Redis"]);
//获取db
var db = conn.GetDatabase(dbIndex);
var listResult = new List<string>();
//遍历集群内服务器
foreach (var endPoint in conn.GetEndPoints())
{
//获取指定服务器
var server = conn.GetServer(endPoint);
//在指定服务器上使用 keys 或者 scan 命令来遍历key
foreach (var key in server.Keys(dbIndex, Extension.RedisInstanceName + keyStr))
{
if (trimRedisInstanceName)
{
listResult.Add(key.ToString().Replace(Extension.RedisInstanceName, ""));
}
else
{
listResult.Add(key);
}
//获取key对于的值
//var val = db.StringGet(key);
Console.WriteLine($"key: {key}, value:");
}
}
return listResult;
}
In the method,Extension.RedisInstanceName used in
services.AddStackExchangeRedisCache(options =>
{
options.Configuration = config.GetSection("Cache")["Redis"];
options.InstanceName = RedisInstanceName;
});
it used by this:
//刷新缓存
var allCacheCompany = await FilterByKey("xxxx.*");
foreach (var companyKey in allCacheCompany)
{
await _cache.RemoveAsync(companyKey);
}

Exceptions in C#

I am trying to write a well-documented code that will be also easy to debug if some exception is handled. Therefore my methods throw exceptions and they're gathered in the log that I can browse. However, it is not really suitable to write complex messages when throwing a new exception. I would like to write a simple utility that would gather:
name of the current class
name of the current method
parameters of the method
Can this be achieved in some easy way? Also, is there a better way to make such logs of exceptions? Perhaps this issue is being solved in a different way, so please share your experience with me :)

An exception already contains this information in its StackTrace.
To get access to it, simply use the public getter:
catch(Exception ex)
{
string trace = ex.StackTrace;
}
If you want to log it, most loggers have an overload which takes an exception. The message and stack trace will be logged.
For example, with log4net, you can use the method void Error(object message, Exception t);:
catch(Exception ex)
{
logger.Error("More details", ex);
}

hi to get the name of the method with signatures the fix is
//get the stack trace
StackTrace stackTrace = new StackTrace();
//the count may vary
MethodBase CallingMethod = stackTrace.GetFrame(2).GetMethod();
//Method called by
string _signatures = MethodInfoExtensions.GetSignature((MethodInfo)CallingMethod));
and the class
public static class MethodInfoExtensions
{
/// <summary>
/// Return the method signature as a string.
/// </summary>
/// <param name="method">The Method</param>
/// <param name="callable">Return as an callable string(public void a(string b) would return a(b))</param>
/// <returns>Method signature</returns>
public static string GetSignature(this MethodInfo method, bool callable = false)
{
var firstParam = true;
var sigBuilder = new StringBuilder();
if (callable == false)
{
if (method.IsPublic)
sigBuilder.Append("public ");
else if (method.IsPrivate)
sigBuilder.Append("private ");
else if (method.IsAssembly)
sigBuilder.Append("internal ");
if (method.IsFamily)
sigBuilder.Append("protected ");
if (method.IsStatic)
sigBuilder.Append("static ");
sigBuilder.Append(TypeName(method.ReturnType));
sigBuilder.Append(' ');
}
sigBuilder.Append(method.Name);
// Add method generics
if (method.IsGenericMethod)
{
sigBuilder.Append("<");
foreach (var g in method.GetGenericArguments())
{
if (firstParam)
firstParam = false;
else
sigBuilder.Append(", ");
sigBuilder.Append(TypeName(g));
}
sigBuilder.Append(">");
}
sigBuilder.Append("(");
firstParam = true;
var secondParam = false;
foreach (var param in method.GetParameters())
{
if (firstParam)
{
firstParam = false;
if (method.IsDefined(typeof(System.Runtime.CompilerServices.ExtensionAttribute), false))
{
if (callable)
{
secondParam = true;
continue;
}
sigBuilder.Append("this ");
}
}
else if (secondParam == true)
secondParam = false;
else
sigBuilder.Append(", ");
if (param.ParameterType.IsByRef)
sigBuilder.Append("ref ");
else if (param.IsOut)
sigBuilder.Append("out ");
if (!callable)
{
sigBuilder.Append(TypeName(param.ParameterType));
sigBuilder.Append(' ');
}
sigBuilder.Append(param.Name);
}
sigBuilder.Append(")");
return sigBuilder.ToString();
}
/// <summary>
/// Get full type name with full namespace names
/// </summary>
/// <param name="type">Type. May be generic or nullable</param>
/// <returns>Full type name, fully qualified namespaces</returns>
public static string TypeName(Type type)
{
var nullableType = Nullable.GetUnderlyingType(type);
if (nullableType != null)
return nullableType.Name + "?";
if (!type.IsGenericType)
switch (type.Name)
{
case "String": return "string";
case "Int32": return "int";
case "Decimal": return "decimal";
case "Object": return "object";
case "Void": return "void";
default:
{
return string.IsNullOrWhiteSpace(type.FullName) ? type.Name : type.FullName;
}
}
var sb = new StringBuilder(type.Name.Substring(0,
type.Name.IndexOf('`'))
);
sb.Append('<');
var first = true;
foreach (var t in type.GetGenericArguments())
{
if (!first)
sb.Append(',');
sb.Append(TypeName(t));
first = false;
}
sb.Append('>');
return sb.ToString();
}
}

The remote host closed the connection. The error code is 0x800703E3

I am currently trying to generate a CSV using nhibernate. This error does not occur on my development enviroment but it does on the live site that it's being used on. I have tried fiddling with time out's but this does not seem to have any effect as it's timing out way before it should. The timing is completely random, sometimes it'll be 3 seconds before it times out the next it will be 10 seconds. There doesn't seem to be any real consistancy in the timing.
Stack Trace:
System.Web.HttpException: The remote host closed the connection. The error code is 0x800703E3.
at System.Web.Hosting.IIS7WorkerRequest.RaiseCommunicationError(Int32 result, Boolean throwOnDisconnect)
at System.Web.Hosting.IIS7WorkerRequest.ExplicitFlush()
at System.Web.HttpResponse.Flush(Boolean finalFlush)
at Reports.CustomCSVWriter.WritetoHttpStream(String filename, Boolean header)
The code is as follows:
public class ProductSpreadSheetDownload : CustomCSVWriter
{
protected override string[] GetCollection()
{
Page.Server.ScriptTimeout = 300;
IList<Product> products = new List<Product>();
IStockScheme stockScheme = Fabric.ObjectProvider.Get<IStockScheme>();
ICriteria criteria = CoreHttpModule.Session.CreateCriteria(typeof(Product))
.Add(NHibernate.Expression.Expression.IsNotNull(Product.STOCK_CODE))
.Add(NHibernate.Expression.Expression.Eq(Product.IS_VISIBLE_ON_WEBSITE, true))
.Add(NHibernate.Expression.Expression.Eq(Product.STOCK_TYPE, StockType.StockItem))
.Add(NHibernate.Expression.Expression.Not(NHibernate.Expression.Expression.Like(Product.NAME, "%*%")));
AddCustomCriteria(criteria);
products = criteria.List<Product>();
products = Product.RemoveOrphanedAndUnrooted((List<Product>)products);
Product[] productArray = new Product[products.Count];
products.CopyTo(productArray, 0);
double?[] levels = stockScheme.GetStock(productArray, false);
List<string> productStringList = new List<string>();
IProductMapper mapper = Fabric.ObjectProvider.Get<IProductMapper>();
var rootUrl = Fabric.SettingsProvider.ReadSetting<string>("RootUrl", string.Empty);
string showOutOfStock = Page.Request.QueryString["ShowOutOfStock"];
int minStockLevel = int.MinValue;
if (showOutOfStock == "False")
minStockLevel = 0;
for (int i = 0; i < productArray.Length; i++)
{
if (levels[i] > minStockLevel && levels[i] != null && productArray[i].Parent != null && productArray[i].Parent.IsVisibleOnWebsite)
{
StringBuilder productStringBuilder = new StringBuilder();
productStringBuilder.AppendFormat("{0}, ", CleanString(productArray[i].Name));
productStringBuilder.AppendFormat("{0}, ", CleanString(productArray[i].StockCode));
productStringBuilder.AppendFormat("{0}, ", levels[i]);
productStringBuilder.AppendFormat("{0}, ", mapper.GetUrl(productArray[i]) );
productStringBuilder.AppendFormat("{0}, ", CleanString(productArray[i].Category));
productStringBuilder.AppendFormat("{0}, ", CleanString(productArray[i].SubCategory));
productStringBuilder.AppendFormat("{0}, ", CleanString(mapper.GetText(productArray[i], "Description")));
productStringBuilder.AppendFormat("{0}, ", mapper.GetImageUrl(productArray[i], "Main"));
AddCustomFields(productStringBuilder, mapper);
productStringList.Add(productStringBuilder.ToString().Trim().TrimEnd(','));
}
}
string[] productstrings = new string[productStringList.Count];
productStringList.CopyTo(productstrings, 0);
return productstrings;
}
/// <summary>
/// Override this method to add custom criteria to the feed
/// </summary>
/// <example>
/// criteria.Add(NHibernate.Expression.Expression.Eq(Product.IS_VISIBLE_ON_WEBSITE, true));
/// </example>
protected virtual void AddCustomCriteria(ICriteria criteria) {}
/// <summary>
/// Override this method to add custom fields to the CSV output
/// </summary>
/// <example>
/// productStringBuilder.AppendFormat("{0}, ", mapper.GetImageUrl(productArray[i], "Main"));
/// </example>
protected virtual void AddCustomFields(StringBuilder productStringBuilder, IProductMapper mapper) { }
protected override string Headers()
{
string headers = "Name, Stockcode, Stock_Level, URL, Category, SubCategory, Description, Main Image URL";
return headers;
}
/// <summary>
/// Removes characters that are not safe in a CSV file.
/// </summary>
protected static string CleanString(string stringToClean)
{
return string.IsNullOrEmpty(stringToClean) ? string.Empty : stringToClean.Replace("\n", " ").Replace(',', ' ');
}
}
}

How to return JSON to browser from model class using SignalR and URL call to Web API?

Here's what's going on. I have an ASP.NET MVC 4 Web API web application. I can call API resources via URL. One of these functions get performance monitoring data for a specified amount of time and returns it in JSON once it has completed. However, what I want to do is return
It is IMPORTANT to note that I am working with a the browser and API resources in the model, not with a View. Please don't casually tell me to use Javascript in a View, because there is no view, or tell me to look at the SignalR wiki because the information for ".NET" sections is meant for desktop applications, not web apps. For example, you can't "Console.WriteLine()" to a browser.
To reiterate, I am using ASP.NET MVC 4 Web API to develop an API, and am calling the API via URL in the browser and it is returning JSON. I am attempting to use SignalR to have the app send JSON to the browser, but it is not doing anything at all. Rather, the application simply returns the completed JSON from the controller action with all of the performance data values once the process has completed. In other words, SignalR is not working.
So what I'm trying to do is while the API resource is gathering all the information, SignalR sends JSON to the browser every second so that the client can see what's going on in real time.
What I need to find out is why SignalR isn't sending it, and how I can send information to be displayed in the browser without Javascript, since I'm working from a model class, not from a view.
As you can see, I subscribe to the event using On, and then use Invoke to call the server-side hub method SendToClient.
Please let me know if I'm trying to do is impossible. I have never heard of a "real-time", dynamic API call via URL.
Here is my hub class. It is located in ~/signalr/hubs and is in a file called LiveHub.cs. The method Send is what I am trying to invoke in the method seen in the next code block.
namespace PerfMon2.signalr.hubs
{
public class LiveHub : Hub
{
public void SendToClient(List<DataValueInfo> json)
{
Clients.showValue(json);
}
}
}
Here is the method from LogDBRepository.cs that includes the SignalR calls.
public List<LogInfo> LogTimedPerfData(string macName, string categoryName, string counterName,
string instanceName, string logName, string live, long? seconds)
{
iModsDBRepository modsDB = new iModsDBRepository();
List<MachineInfo> theMac = modsDB.GetMachineByName(macName);
if (theMac.Count == 0)
return new List<LogInfo>();
else if (instanceName == null)
{
if (!PerformanceCounterCategory.Exists(categoryName, macName) ||
!PerformanceCounterCategory.CounterExists(counterName, categoryName, macName) )
{
return new List<LogInfo>();
}
}
else if (instanceName != null)
{
if (!PerformanceCounterCategory.Exists(categoryName, macName) ||
!PerformanceCounterCategory.CounterExists(counterName, categoryName, macName) ||
!PerformanceCounterCategory.InstanceExists(instanceName, categoryName, macName))
{
return new List<LogInfo>();
}
}
else if (logName == null)
{
return new List<LogInfo>();
}
// Check if entered log name is a duplicate for the authenticated user
List<LogInfo> checkDuplicateLog = this.GetSingleLog(logName);
if (checkDuplicateLog.Count > 0)
{
return new List<LogInfo>();
}
PerformanceCounterCategory category = new PerformanceCounterCategory(categoryName, theMac[0].MachineName);
if (category.CategoryName == null || category.MachineName == null)
{
return new List<LogInfo>();
}
List<LogInfo> logIt = new List<LogInfo>();
if (category.CategoryType != PerformanceCounterCategoryType.SingleInstance)
{
List<InstanceInfo> instances = modsDB.GetInstancesFromCatMacName(theMac[0].MachineName, category.CategoryName);
foreach (InstanceInfo inst in instances)
{
if (!category.InstanceExists(inst.InstanceName))
{
continue;
}
else if (inst.InstanceName.Equals(instanceName, StringComparison.OrdinalIgnoreCase))
{
PerformanceCounter perfCounter = new PerformanceCounter(categoryName, counterName,
inst.InstanceName, theMac[0].MachineName);
//CounterSample data = perfCounter.NextSample();
//double value = CounterSample.Calculate(data, perfCounter.NextSample());
string data = "";
List<UserInfo> currUser = this.GetUserByName(WindowsIdentity.GetCurrent().Name);
string timeStarted = DateTime.Now.ToString("MM/dd/yyyy - h:mm:ss tt");
//string[] dataValues = new string[(int)seconds];
List<string> dataValues = new List<string>();
var hubConnection = new HubConnection("http://localhost/PerfMon2/");
hubConnection.Credentials = CredentialCache.DefaultNetworkCredentials;
var perfMon = hubConnection.CreateProxy("LiveHub");
// perfMon.On("sendValue", message => Console.WriteLine(message));
perfMon.On("showValue", json => Console.WriteLine(json));
hubConnection.Start().Wait();
List<DataValueInfo> lol = new List<DataValueInfo>();
for (int i = 0; i < seconds; i++)
{
data = "Value " + i + ": " + perfCounter.NextValue().ToString();
//dataValues[i] = data;
dataValues.Add(data);
lol.Add(new DataValueInfo
{
Value = perfCounter.NextValue().ToString()
});
// perfMon.Invoke<List<DataValueInfo>>("Send", lol);
perfMon.Invoke("SendToClient", lol);
Thread.Sleep(1000);
}
string timeFinished = DateTime.Now.ToString("MM/dd/yyyy - h:mm:ss tt");
Log log = new Log
{
LogName = logName,
CounterName = perfCounter.CounterName,
InstanceName = perfCounter.InstanceName,
CategoryName = perfCounter.CategoryName,
MachineName = perfCounter.MachineName,
TimeStarted = timeStarted,
TimeFinished = timeFinished,
PerformanceData = string.Join(",", dataValues),
UserID = currUser[0].UserID
};
this.CreateLog(log);
logIt.Add(new LogInfo
{
LogName = logName,
CounterName = perfCounter.CounterName,
InstanceName = perfCounter.InstanceName,
CategoryName = perfCounter.CategoryName,
MachineName = perfCounter.MachineName,
TimeStarted = timeStarted,
TimeFinished = timeFinished,
PerformanceData = dataValues.ToList<string>()
});
break;
}
}
}
else
{
PerformanceCounter perfCounter = new PerformanceCounter(categoryName, counterName,
"", theMac[0].MachineName);
string data = "";
List<UserInfo> currUser = this.GetUserByName(WindowsIdentity.GetCurrent().Name);
string timeStarted = DateTime.Now.ToString("MM/dd/yyyy - h:mm:ss tt");
//string[] dataValues = new string[(int)seconds];
List<string> dataValues = new List<string>();
var hubConnection = new HubConnection("http://localhost/PerfMon2/");
hubConnection.Credentials = CredentialCache.DefaultNetworkCredentials;
var perfMon = hubConnection.CreateProxy("LiveHub");
// perfMon.On("sendValue", message => Console.WriteLine(message));
perfMon.On("showValue", json => Console.WriteLine(json));
hubConnection.Start().Wait();
List<DataValueInfo> lol = new List<DataValueInfo>();
for (int i = 0; i < seconds; i++)
{
data = "Value " + i + ": " + perfCounter.NextValue().ToString();
//dataValues[i] = data;
dataValues.Add(data);
lol.Add(new DataValueInfo
{
Value = perfCounter.NextValue().ToString()
});
// perfMon.Invoke<List<DataValueInfo>>("Send", lol);
perfMon.Invoke("SendToClient", lol);
Thread.Sleep(1000);
}
string timeFinished = DateTime.Now.ToString("MM/dd/yyyy - h:mm:ss tt");
Log log = new Log
{
LogName = logName,
CounterName = perfCounter.CounterName,
InstanceName = perfCounter.InstanceName,
CategoryName = perfCounter.CategoryName,
MachineName = perfCounter.MachineName,
TimeStarted = timeStarted,
TimeFinished = timeFinished,
PerformanceData = string.Join(",", dataValues),
UserID = currUser[0].UserID
};
this.CreateLog(log);
logIt.Add(new LogInfo
{
LogName = logName,
CounterName = perfCounter.CounterName,
InstanceName = perfCounter.InstanceName,
CategoryName = perfCounter.CategoryName,
MachineName = perfCounter.MachineName,
TimeStarted = timeStarted,
TimeFinished = timeFinished,
PerformanceData = dataValues.ToList<string>()
});
}
return logIt;
}
Here is the controller for the method in LogController.cs :
[AcceptVerbs("GET", "POST")]
public List<LogInfo> Log_Perf_Data(string machine_name, string category_name, string counter_name, string instance_name,
string log_name, long? seconds, string live, string enforceQuery)
{
LogController.CheckUser();
// POST api/log/post_data?machine_name=&category_name=&counter_name=&instance_name=&log_name=&seconds=
if (machine_name != null && category_name != null && counter_name != null && log_name != null && seconds.HasValue && enforceQuery == null)
{
List<LogInfo> dataVal = logDB.LogTimedPerfData(machine_name, category_name, counter_name, instance_name,
log_name, live, seconds);
logDB.SaveChanges();
return dataVal;
}
return new List<LogInfo>();
}

Maybe you can implement it in push technique. Here is how I do it:
Class with message
public class Message
{
/// <summary>
/// The name who will receive this message.
/// </summary>
public string RecipientName { get; set; }
/// <summary>
/// The message content.
/// </summary>
public string MessageContent { get; set; }
}
Class that will represent client:
public class Client
{
private ManualResetEvent messageEvent = new ManualResetEvent(false);
private Queue<Message> messageQueue = new Queue<Message>();
/// <summary>
/// This method is called by a sender to send a message to this client.
/// </summary>
/// <param name="message">the new message</param>
public void EnqueueMessage(Message message)
{
lock (messageQueue)
{
messageQueue.Enqueue(message);
// Set a new message event.
messageEvent.Set();
}
}
/// <summary>
/// This method is called by the client to receive messages from the message queue.
/// If no message, it will wait until a new message is inserted.
/// </summary>
/// <returns>the unread message</returns>
public Message DequeueMessage()
{
// Wait until a new message.
messageEvent.WaitOne();
lock (messageQueue)
{
if (messageQueue.Count == 1)
{
messageEvent.Reset();
}
return messageQueue.Dequeue();
}
}
}
Class to send messages to clients:
public class ClientAdapter
{
/// <summary>
/// The recipient list.
/// </summary>
private Dictionary<string, Client> recipients = new Dictionary<string,Client>();
/// <summary>
/// Send a message to a particular recipient.
/// </summary>
public void SendMessage(Message message)
{
if (recipients.ContainsKey(message.RecipientName))
{
Client client = recipients[message.RecipientName];
client.EnqueueMessage(message);
}
}
/// <summary>
/// Called by a individual recipient to wait and receive a message.
/// </summary>
/// <returns>The message content</returns>
public string GetMessage(string userName)
{
string messageContent = string.Empty;
if (recipients.ContainsKey(userName))
{
Client client = recipients[userName];
messageContent = client.DequeueMessage().MessageContent;
}
return messageContent;
}
/// <summary>
/// Join a user to the recipient list.
/// </summary>
public void Join(string userName)
{
recipients[userName] = new Client();
}
/// <summary>
/// Singleton pattern.
/// This pattern will ensure there is only one instance of this class in the system.
/// </summary>
public static ClientAdapter Instance = new ClientAdapter();
private ClientAdapter() { }
}
Sending messages:
Message message = new Message
{
RecipientName = tbRecipientName.Text.Trim(),
MessageContent = tbMessageContent.Text.Trim()
};
if (!string.IsNullOrWhiteSpace(message.RecipientName) && !string.IsNullOrEmpty(message.MessageContent))
{
// Call the client adapter to send the message to the particular recipient instantly.
ClientAdapter.Instance.SendMessage(message);
}
Receive messages (this is JavaScript functions written in test page. They render content of the message on ASPX page. Here you should implement your logic):
// This method will persist a http request and wait for messages.
function waitEvent() {
CSASPNETReverseAJAX.Dispatcher.WaitMessage("<%= Session["userName"] %>",
function (result) {
displayMessage(result);
// Keep looping.
setTimeout(waitEvent, 0);
}, function () {
// Keep looping.
setTimeout(waitEvent, 0);
});
}
// Append a message content to the result panel.
function displayMessage(message) {
var panel = document.getElementById("<%= lbMessages.ClientID %>");
panel.innerHTML += currentTime() + ": " + message + "<br />";
}
// Return a current time string.
function currentTime() {
var currentDate = new Date();
return currentDate.getHours() + ":" + currentDate.getMinutes() + ":" + currentDate.getSeconds();
}