Category Archives: dotNet Product

Generate password node for SoftEther config file

Recently, I wrote an C# project for connect all devices from clients of my company to the server for remotely fault detection. SoftEther is chosen for underlying network solution.

The maintenance engineers don’t want to use the GUI of SoftEther to create profiles for each clients. A project is required for generating config files.

The only problem is how SoftEther store the password. I dig a lot and got the answer.

  • Password is encrypted by SHA0 on password + USERNAME in capital.
  • NTLM related password is encrypted by MD4.


Here is the password node generating project, based on C#, dotnet core 3. Actually, the code is tested on dotnet core 2 and netfx 4 also.

Multiple Low-end bar code scanners support for dotNet

Adds support for low end bar code scanners, which work as a keyboard only. By using this library, you can receive code from multiple scanners with the scanner handle id or name (seeing demo on Github).

Platform: dotNet Framework 4 on Windows x86, or x64 with 32-bit compiling (need 32-bit due to WinAPI calling)

Package: Nuget

Source code: Github

License: Demo and Test projects are licensed under MIT. Main and other libraries are licensed under LGPLv3.

dotNet Library: Fraction Support

Add fraction support.

Known Issue:

Using an instance built by default parameterless constructor will cause exception or miscalculation. To avoid this, always use parameter-based constructors. This will not be fixed due to consideration about running speed.

Source code: Github

License: MIT

Nuget: fraction

Supported platform: NetCore 1, NetCore 2, NetFx 4, NetStd 1.3, NetStd 2.0


A replacement of NetFx Threading.Timer without cumulative error

This is a complete replacement of Threading.Timer. All methods of Threading.Timer are supported. You could use this TimerFix by simply replacing the Threading.Timer object.

Threading.Timer is encapsulated in this class.

In constructors, you could pass the interval setting value. Less the value set, more CPU time is required. Default value is 15 milliseconds.


Source code: Github

License: MIT

Nuget: SecretNest.TimerFix

Supported platform: NetCore 1, NetCore 2, NetFx 4, NetStd 1.3, NetStd 2.0

A way to run nearly all functions of dotNet from SQL Server

Last night, I got a case to write a function in SQL Server 2005 to support the user account and password check against Active Directory. The user requirement is quite clear:

  • Create a scalar-valued function named LDAPUserCheck;
  • Parameter @username nvarchar(MAX) for user name to check;
  • Parameter @password nvarchar(MAX) for password matching the username specified;
  • Return bit 1 if succeeded, or 0 for all other reasons.

After a digging, I found that LDAP password authentication is not supported directly by SQL Server. But SQLCLR is a way to build the native dotnet program into SQL Server. In a new created SQLCLR project in VS 2005, I realized it’s unable to add the reference System.DirectoryServices.AccountManagement, which is required by running the code for Active Directory authentication. But a Web Service is a choice.

My steps to achieve that:

1 Create and deploy a Web Service for the authentication check.

1.1 Create a Web Service project.

1.2 Add System.DirectoryServices.AccountManagement as a reference.

1.3 Add a setting DomainName as string for storing the domain name.

1.4 Add a service like this:

    public class LDAPAuthentication : System.Web.Services.WebService
        static string domainName = Settings.Default.DomainName;

        public bool Check(string userName, string password)
            using (PrincipalContext pc = new PrincipalContext(ContextType.Domain, domainName))
                // validate the credentials
                bool isValid = pc.ValidateCredentials(userName, password);
                return isValid;

1.5 Deploy this service and use a application pool running by a domain user. This user should be added to IIS_WPG group in Windows Server 2003.

2 Create a SQLCLR project to call the Web Service.

2.1 Create a SQLCLR project in Visual Studio 2005.

2.2 Add a Web Service reference. It’s named as LDAP in my project.

2.3 Add a User Defined Functions.

    public static SqlBoolean LDAPUserCheck(
        SqlString username, SqlString password)
        using (LDAPAuthentication.LDAP.LDAPAuthentication service = new LDAPAuthentication.LDAP.LDAPAuthentication())
            if (service.Check(username.ToString(), password.ToString()))
                return SqlBoolean.True;
                return SqlBoolean.False;

2.4 Set Permission Level to External in Database page of project setting.

2.5 Build this project to get the dll files. In my case, these files are named LDAPAuthentication.dll and LDAPAuthentication.XmlSerializers.dll.

3 Deploy this project into SQL Server 2005.

3.1 Enable the CLR support in SQL Server 2005 by running this code:

sp_configure 'show advanced options', 1;

sp_configure 'clr enabled', 1;

sp_configure 'show advanced options', 0;

3.2 Create a database for storing this function. Or, you can use any existed database as well. In my case, I created a database “tester”.

3.3 Set trustworthy on this database by running:

ALTER DATABASE [tester] SET trustworthy ON

3.4 Copy the 2 dll files created in step 2 to this server. In my case, these are stored in C:\SQLCLR folder.

3.5 Create assemblies in SQL Server by running:

create assembly [LDAPAuthentication] from 'C:\SQLCLR\LDAPAuthentication.dll' with permission_set = external_access
create assembly [LDAPAuthentication.XmlSerializers] from 'C:\SQLCLR\LDAPAuthentication.XmlSerializers.dll' with permission_set = external_access

3.6 Create function to run the method we’ve created in VS 2005:

CREATE FUNCTION [dbo].[LDAPUserCheck](@username [nvarchar](4000), @password [nvarchar](4000))
EXTERNAL NAME [LDAPAuthentication].[UserDefinedFunctions].[LDAPUserCheck]

Now everything is done. You can call this function like all others created by SQL. Run this for test.

select dbo.LDAPUserCheck('myusername','mypassword')


Solved: Why Linq Where.FirstOrDefault is faster than use FirstOrDefault with condition on an array?

Hi all.


Why applying “.Where(condition).FirstOrDefault()” is much faster than “.FirstOrDefault(condition) when it’s applied on an array?


Answer: While calling method Where() on an Array or a List, it’s optimized to use the enumerator of the source directly. But FirstOrDefault(), which doesn’t have this mechanism, runs the virtual method version from IEnumerator.GetEnumerator().

Special thanks to Iris Sakura.

C#: Convert a tree node and sub nodes to text

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace TreeToText
    class TreeToText
        const string LineMid = "├─";
        const string LineLast = "└─";
        const string Line = "│  ";
        const string Space = "    ";

        /// <summary>
        /// Convert a tree node to text
        /// </summary>
        /// <param name="node">Root node to convert</param>
        /// <returns>Text</returns>
        public static string Tree2Text(TreeNode node)
            if (node == null) return null;
            StringBuilder builder = new StringBuilder();
            Tree2Text(builder, node, "");
            return builder.ToString();

        static string TreeNodeText(TreeNode node)
            return node.Text;

        static void Tree2Text(StringBuilder builder, TreeNode parent, string prefix)
            int nodesCount = parent.Nodes.Count;
            if (nodesCount == 0) return;
            int nodeMaxIndex = nodesCount - 1;
            for (int i = 0; i < nodesCount; i++)
                TreeNode node = parent.Nodes[i];
                if (i != nodeMaxIndex)
                    Tree2Text(builder, node, prefix + Line);
                    Tree2Text(builder, node, prefix + Space);