DOT NET developer blog: May 2020

Lazy Logger

Scenario:

Logger with Lazy loading

Solution:

Loading Logger when needed

using System.Collections;
namespace Web.Models
{
    public static class Class
    {
        private static readonly Lazy<Logger> Logger;

        public static Class()
        {
            Logger = new Lazy<Logger>(() =>
               Get<ILoggerFactory>().GetLogger()));
        }
        public bool Validate()
        {
            Logger.Value.Error(e, $"Error")
        }
    }
}

Regular Expressions

Scenario:

Various regular expression scenarios

Solution:

Hex Character
var rex = new Regex("[0-9,A-F,a-f]{2}");
Line Breaks 
var rex = new Regex(@"[\r\n\t]");

File name "${RND:###}-${TS:yyyyMMdd}.${RND:#}.csv";

var fileFormat = new Regex(@"\${(?<type>(RANDOM|TIMESTAMP)):(?<format>[^}]+)}",
            RegexOptions.Compiled | RegexOptions.CultureInvariant | RegexOptions.IgnoreCase);

```
Replace
```

var regex = new Regex(@"""(\d+\.\d)""", RegexOptions.Compiled);

response = regex.Replace(response, @"""percent$1""");

"fieldName[]"

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20 using System.Text.RegularExpressions;

namespace Web.Models
{
    public class Class
    {
        public bool Validate()
        {
            var value = "fieldName[]";
            var regex = new Regex(@"^fieldName\[.*?\]$",
                   RegexOptions.Compiled | RegexOptions.IgnoreCase | RegexOptions.CultureInvariant);

            if (regex.IsMatch(value))
            {
                return true;
            }
            return false;
        }
    }
}

Validate query string and value based on if query string is present

Scenario:

Validate query string for null or empty if only it exists

Solution:

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11  public bool validate()
        {
            if (queryStringCollection.AllKeys.Any(k => k.StartsWith("field_name")))
            {
                fieldValue = queryStringCollection.Get("field_name");
                if (string.IsNullOrWhiteSpace(fieldValue) )
                {
                    throw customeError;
                }
            }
        }

Identify the correct w3wp process to attach while debugging in Visual Studio

Scenario:

Identify the correct w3wp process to attach while debugging in Visual Studio

Solution:

Open command prompt and run below command. Find the ID (number) of your application pool and look for that ID while attaching w3wp in VS.

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3 cd C:\Windows\System32\inetsrv\

appcmd.exe list wp

Ignore Ssl validation error while connecting to https endpoint

Scenario:

Ignore Ssl validation error while connecting to https endpoint.

Solution:

Ignore ssl validaton errors and continue. In cases where the endpoints are internal only and so CA(Certificating Authority) wont verify and issue a SSL. In such cases certificate used is self-signed one. Below is setting at instance level. Add this before creating HttpClient.

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7 var handler = new HttpClientHandler();

                    handler.SslProtocols = SslProtocols.Tls | SslProtocols.Tls11 | SslProtocols.Tls12;
                    handler.ServerCertificateCustomValidationCallback = delegate { return true; };

                
var httpClient= new HttpClient(handler);

Ignore ssl validaton errors and continue. In cases where the endpoints are internal only and so CA(Certificating Authority) wont verify and issue a SSL. In such cases certificate used is self-signed one. Below is the global change. Add this before creating HttpClient.

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5 // wrap this in config

ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
                ServicePointManager.ServerCertificateValidationCallback +=
                    (sender, cert, chain, sslPolicyErrors) => true;

Add Certificate to mmc

Scenario:

Add a Certificate to mmc.

Solution:

Windows -> run -> mmc
File -> Add Remove snap-ins -> Certificates -> Add -> Ok
Expand Certificates -> Intermediate Certification Authority -> right click -> All Tasks -> import.
In menu -> Next -> Browse to certificate -> Next -> Finish.
To add/look at permission: Select certificate -> more actions -> all tasks.
In IIS, go to site -> Server Certificates ->

The Certificate should be added under Intermediate Certification Authority/Personal now.

Configure LogStash on docker

Scenario:

Configure LogStash on docker.

Solution:

Access and login to core os, in command line
ls
cd elasticsearch
cd logstashpipeline
vim api.confg (longstash configuration file)

input {

redis {

codec => "json"

data_type => "list"

host => "redis"

key => "api"

port => "6379"

tags => ["local"]

add_field => {"origin" => "myapp-api-local"}

}

output {

if " myapp-api-local " in [origin] {

elasticsearch {

action => "index"

hosts => ["http://elasticsearch:9200"]

index => "logstash-myapp-api-%{+YYYY.MM.dd}"

}

:wq
cd ..
cat stop.sh
./stop.sh
./start.sh
git status
git add *
git status
git commit -a -m "Comments"
git push

In Vim

Hit the Esc key to enter Normal mode and type : for Command line mode.

· :q - quit

· :q! - quit

· :wq - write and quit

· qa – quit instance

· i – insert mode

· dd to delete line

· dw to delete single word

· Delete key to delete characters

Jump servers

Scenario:

You are not able to connect to a host, you can use aws etc to jump servers to access the sites/endpoints.

Solution:

Open PuTTY
Session -> Create new (amazon core os host name) -> Host Name [amazon host name] -> Save
Session -> Select: amazon -> Load -> Left nav -> SSH -> Tunnels
Add Source port & Destination combinations (IIS should not have any site running on 80/443, else stop that), e.g.:

5601 , 10.20.20.20:5601
443 , 10.20.20.20:443
80 , 10.20.20.20:80

Go to host file (as administrator), add entries for site with i/p: 10.20.20.20 replaced with 127.01.0.1 -> Save.
PuTTY -> Session -> select: amazon -> double click
Provide login & password

Now you should be able to navigate to endpoints as before, this is jumping servers.

Floccus bookmarks

Scenario:

To share bookmarks with team members, Floccus provides self hosted solution.

Solution:

DNS to hosts.
Install floccus extension for Chrome: https://chrome.google.com/webstore/detail/floccus-bookmarks-sync/fnaicdffflnofjppbagibeoednhnbjhg?hl=en
Add a new folder to the bookmark bar
Configuration:

Add account
Select Nextclould Bookmarks
Nextcloud URL: http://nextcloud.mpls.digitalriver.com

Username: {user}
Password: {password}

Local folder: Choose Folder -> newly created folder above
Save
Enabled is checked
Click Sync

Push data to Redis - test using docker container

Scenario:

Follow below steps:

Portainer host -> local -> Containers -> Container -> Redis
Redis command prompt
cd /usr/local/bin enter
ls enter
redis-cli -h hostname -p port
KEYS *

All Keys still in queue or stuck to be consumed

LLEN keyname

If there are any still in queue or stuck to be consumed

To connect without redis-cli use below:

ncat -v --ssl redisendpoint 6379 --if not on ssl, remove ssl option
To close connection ctrl + D

DELETE Key

DEL KeyName

Redis ConnectionMultiplexer

Scenario:

Stackexchange.Redis.ConnectionMultiplexer hides the details of multiple servers and shared and reused between callers. It is thread-safe and ready for this usage.

Solution:



 

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private TResult SendData<TResult>(Func<ConnectionMultiplexer, TResult> call)
        {
            _lock.EnterReadLock();
            try
            {
                if (_redis != null)
                {
                    return call(_redis);
                }
            }
            finally
            {
                _lock.ExitReadLock();
            }

            _lock.EnterWriteLock();
            try
            {
                if (_redis != null)
                {
                    return call(_redis);
                }

                _redis =
                    ConnectionMultiplexer.Connect(
                        $"{string.Join(",", Servers.Select(c => $"{c.Server}:{c.Port}"))}{(string.IsNullOrWhiteSpace(ServerOptions) ? "" : $",{.ServerOptions}")}");
                
                _redis.PreserveAsyncOrder = false;

                return call(_redis);
            }
            finally
            {
                _lockSlim.ExitWriteLock();
            }
        }

Access properties of model on Generic method

Scenario:

We want to edit model before further processing. The model is passed to a Generic method. Also name of Datamember of the model has to be different than property name.

Solution:



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        public interface IModel
        {
            string Filename { get; set; }
        }

        public class Model : IModel
        {
            [DataMember(Name = "fileName")]
            public string FileName { get; set; }
        }


 

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    public abstract class Client<T> : IClient where T : class
    {
        private void Process(T model)
        {
            if (model is IModel model)
            {
                model.Filename = application.FileName;
            }
        }
    }

HttpClient connect with basic authentication

Scenario:

Connect to service using login/password

Solution:

Connect using basic authentication and send message


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            var client = new HttpClient();

            var bytearray = Encoding.ASCII.GetBytes($"{userName}:{password}");
            client.DefaultRequestHeaders.Authorization =
                new AuthenticationHeaderValue("Basic", Convert.ToBase64String(bytearray));

            var response = client.SendAsync(message).Result;

            var statusCode = response.StatusCode;