c# throw windows event

To make a running server-application a way more professional we can not just write our own log about what is going good or bad. We can go instead and use windows events. In the following example I will write a Windows-Event in a created event-source. By doing this I can separate all the events that I will throw out in my applications from the other event-messages and errors of the other applications.

class Program
{
   const string APP_SOURCE = "LiveCodeBlog";
   
   static void Main(string[] args)
   {
      EventLog.CreateEventSource(APP_SOURCE , APP_SOURCE);

      EventLog myLog = new EventLog
      {
         Source = APP_SOURCE
      };

      myLog.WriteEntry("Writing to event log with the source " + APP_SOURCE);

   }
}

The final result looks like this:

However to create a event-source you need to have the rights to do this. Exactly you need full-rights to create the even-source and as well read-rights for all other event sources. This is because .Net wants to check if there is another eventsource named like this. So you can check your right like this:

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c# avoid constructor redundancy

Sometimes we need to define several constructors that just get different types – but all do do same like the following here:

class MyClass
{
   int x;
   public int X { get => x; set => x = value; }

   MyClass(int x)
   {
      this.x = x;
      //... do further things
   }

   MyClass(string x)
   {
      this.x = int.Parse(x);
      //... do other further things
   }
}

But we can do this in a better way by inheriting from one constructor like this:

class MyClass
{
   int x;
   public int X { get => x; set => x = value; }

   MyClass(int x)
   {
      this.x = x;
      //... do further things
   }

   MyClass(string x) : this(int.Parse(x))
   {
      //... do other further things
   }
}

By doing this the string-parameter-constructor inherit the int-parameter-constructor and does every thing. We also could call the int-parameter-constructor -method in the string-parameter-parameter like “this(int.Parse(x))”.

SOAP API in Visual Studio in C#

To create a api there are alot opporunities. Right now I prefer SOAP-APIs in Visual Studio because it is easy as possible to create such one.

I will do this with Visual Studio 2017 and a console-application, so nothing special:

For the example I googled for free SOAP-Webservice and got this one here that can handle some information about the BLZ:

http://www.thomas-bayer.com/axis2/services/BLZService?wsdl

To start in Visual Studio I add a reference like this:

  1. Rightclick in the solution explorer at references.
  2. Click “Add Service Reference”
  3. Click “Advanced…”
  4. Click “Add Web Reference…”
  5. Paste the URL and click on the arrow.
  6. Type in a name that specifies the webservice-name in your project.
  7. Click “Add Reference”.
  8. Done!

<

pre>This will add a folder to your projects called “Web References” and will add the service. Like this you will also get every object and method that you need. So I am able to write this code:

var BLZService = new OpenSOAPBLZService.BLZService();
 var Bank = BLZService.getBank("10070100");
 Console.WriteLine(Bank.bezeichnung + " - " + Bank.ort);
 Console.ReadLine();

 

Here we create a new object based on the service that we created, create a new bank object (which class is also created by the Add-Reference-Function) and show the bank description and the location of the bank in the console. So we get this out here:

how to start with xamarin forms

Lets get some xamarin.forms basics done and check out how we can emulate this with focus to android. Why android focus? My test phone is based on android. So lets start here with some action. For this we need visual studio (in my case 2017 professional). So we create a new project -> Cross Plattform App (Xamarin) -> Emty App -> Xamarin.Forms -> portable class library (PCL). Just do not think to much about it if you are new to xamarin.

Now I choosed CameraApp.Android to debug things:

So visual studio got some emulator if you just installed the xamarin-part. Problem here is that it is incompatible with hyper-v. So if you do not want to disable hyper-v you should the Visual Studio Android Emulator for example. So check out this. With that you can set up some emulators that work with hyper-v without any further problems. I use the 5” KitKat (4.4) XXHDPI Phone. Install that one and it should look like this:

If you got this you should go for 2 further things to avoid problems with dll-uploading:

  • Go to hyper-v -> your new device -> settings -> processor -> compatibility -> and make sure that you put on the migration to other physical computers.
  • In visual-studio -> solution-explorer -> android solution -> properties -> android-options -> disable fast deployment
  • Update alle nuGet packages

So now we have to start our emulator by using the vs-android-emulator. Here we need to enable developer-mode and maybe usb-debugging. Than start debugging in visual studio and you should see the emulator running your code. If you get problems here you always have to check the output in vs. A lot of problems you can not see as a real fail in vs. But instead you get some information in the output-window. As well if you have trouble make sure that all nuget-packages are updated to the correct/last version. BTW: the last version is not the correct version in any case. And another thing that may can confuse you: Rebuild your solution. Sometimes you have to rebuild your solution to make vs get all new things that you did. However you should see something like this:

mysql basics in c#

Today I want to describe how we can work with MySQL-DBs in C#. Before Using queries and other things we have to connect to the database. Todo this set up an MySQLMgt-code-file that contains all things we need to have to work with our database. Here we got some properties like this. To use the MySsqlConnection just include the library “MySql.Data.MySqlClient”.

    static private MySqlConnection connection;
    static private string server;
    static private string database;
    static private string uid;
    static private string password;

I decide to fill these properties in the constructor and connect than to the server:

 
    static MySqlManagement()
    {
        loadServerSettings();
        connectServer();
    }

For sure we can fill the properties hard-coded but I want to make it better and I put the things into the appsettings. Just put in the things you need and you can write these values into the class-properties:

static private void loadServerSettings()
    {
        server = ConfigurationManager.AppSettings["server"];
        database = ConfigurationManager.AppSettings["database"];
        uid = ConfigurationManager.AppSettings["uid"];
        password = ConfigurationManager.AppSettings["password"];
    }

To connect to the server we need a connection-string and a MySQL-Connection.

static private void connectServer()
    {
        string connectionString =
            "SERVER=" + server + ";" +
            "DATABASE=" + database + ";" +
            "UID=" + uid + ";" +
            "PASSWORD=" + password + ";";
 
        connection = new MySqlConnection(connectionString);
 
        try
        {
            connection.Open();
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }

Wit the connection. Open we are able to give some instruction/queries into our database. Here we can insert, modify and delete data or change the structure of the data as well. In the following you will see an easy insert-mysql-stament fired into the mysql-db.

string query = "INSERT INTO link (url, provider_id, posting_datetime) VALUES(" +
                    "'" + url + "', " +
                    "'" + providerId + "', " +
                    "'" + postingDateTime.ToString("yyyy-MM-dd H:mm:ss") + "')";
 
                MySqlCommand cmd = new MySqlCommand(query, connection);
                cmd.ExecuteNonQuery();

Another thing that you should know in term of mysql-c# basics is the use of return value of queries. Here is method that tells me if an entry already exists:

static public bool UrlExists(string url)
       {
           string query = "SELECT COUNT(*) FROM link WHERE url = '" + url + "'";
           MySqlCommand cmd = new MySqlCommand(query, connection);
 
           int Count;
           Count = int.Parse(cmd.ExecuteScalar() + "");
 
           return Count > 0;
       }

@ the end of your code: Make sure to close the connection to the MySQLServer with:

connection.Close();

Have fun with it! 🙂
 

c# webcrawling basics

To download the metadata and the content of a website you have some opportunities like this for example:

HttpWebRequest httpWebRequest = (HttpWebRequest)HttpWebRequest.Create(url);
WebRequest webRequest = (WebRequest)httpWebRequest;
WebResponse webResponse = webRequest.GetResponse();
StreamReader sr = new StreamReader(webResponse.GetResponseStream());
string htmlStr = sr.ReadToEnd();

While doing this you create a http-web-request and a web-response. With the stream-reader you will get the metadata and the content of the website and are able to write this into string.

dynamic read on JSON response in c#

If you want to work with a JSON-formatted response, there are many ways to handle this. In the following I could figure out a dynamic read that will give you the opportunity to use the different types.

The first code-example shows how to download some data with a given URL. For this you will need the assembly “System.Net”:

string url = "address?$format=json";
var webClient = new WebClient();
String jsonResponse = webClient.DownloadString(url);

The second code-example shows how to read out the single attributes. For this you have to include the assembly “Newtonsoft.Json”:

dynamic results = JsonConvert.DeserializeObject(jsonResponse);

string myName = results.Name;
string myFirstName = results.FirstName;
int myAge = results.Age;
//...

After using the JsonConvert.DeserializeObject-function you can use every single attribute.