Tag: .NET

The most performant way of appending two string builders in .NET Framework 4, use this;

frontStringBuilder.Append(backStringBuilder);

For .NET Framework 2.0/3.5, use this;

frontStringBuilder.Append(backStringBuilder.ToString(0, backStringBuilder.Length));

This wouldn’t hurt performance in .NET FW 4.0.

Resources

https://stackoverflow.com/questions/6454392/how-to-append-two-stringbuilders

We want to treat lambda expressions as expression trees and look inside them instead of executing them. For example, LINQ to SQL gets the expression and converts it to the equivalent SQL statement and submits it to server (rather than executing the lambda).

With Lambda expressions we can write less code, and the code will be more readable.

A lambda expression uses the lambda operator => which means goes to.

arguments => expession

The expression reads: arguments goes to expression.

Let’s start with a common example;

using System;

namespace Lambdas
{
    class Program
    {
        static void Main()
        {
            Console.WriteLine(Square(5));
            Console.ReadLine();
        }

        static int Square(int num)
        {
            return num * num;
        }
    }
}

we declare a method called Square of type int with one input parameter of type int. It multiplies the number and returns the result.

In the Main() method we call our Square method with an int as a parameter.

We can convert this function into a Lambda expression. This is what it would look like:

num => num * num;

This expression would read: num goes to calculation (num * num).

This expression is short and easily readable once we get used to it. The catch though, is that a Lambda expression must be assigned to a delegate.

Resources

https://stackoverflow.com/questions/793571/why-would-you-use-expressionfunct-rather-than-funct

https://tyrrrz.me/blog/expression-trees

https://thesharperdev.com/an-introduction-to-c-expression-trees/

Midnight is the first one – It’s the very first second of the day, not the last.

var todayDateTime = DateTime.Today;
var Midnight = todayDateTime.AddSeconds(-1);
//Here are the results
Console.WriteLine($"Today {todayDateTime.ToString()}, Mid night {Midnight.ToString()}");

The output is this;

Today 10/8/2021 12:00:00 AM, Mid night 10/7/2021 11:59:59 PM

I am using EF for most of my ORM and data access. Recently I have tries Dapper and started liking it because of its simplicity and small footprint. Here is a list of example;

Using Dapper to fill a dataset;

Dapper returns a IDataReader when we use the ExecuteReaderAsync method. More information on this addition can be found here and here.

Use Nuget package to add Dapper. Add this to your Main class for quick demo;

static IDbConnection dbConn = new SqlConnection(ConfigurationManager.ConnectionStrings["SqlServerConnString"].ConnectionString);

Here you go with DataSet example using Dapper;

public async Task<DataSet> GetUserInformationOnUserId(int UserId)
{
    var storedprocedure = "usp_getUserInformation";
    var param = new DynamicParameters();
    param.Add("@userId", UserId);
    var list = await SqlMapper.ExecuteReaderAsync(dbConn, storedprocedure, param, commandType: CommandType.StoredProcedure);
    var dataset = ConvertDataReaderToDataSet(list);
    return dataset;
}

Here is conversion to dataset method;

public DataSet ConvertDataReaderToDataSet(IDataReader data)
{
    DataSet ds = new DataSet();
    int i = 0;
    while (!data.IsClosed)
    {
        ds.Tables.Add("Table" + (i + 1));
        ds.EnforceConstraints = false;
        ds.Tables[i].Load(data);
        i++;
    }                    
    return ds;
}

How to map class names to class properties with dapper

Manually map column name with class properties

Does Dapper supports .NET DataSets

Here you go;

In your Startup.cs, under the Configure method, add the following line:

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
app.UseSession();
}

And under the ConfigureServices method, add the following line:

public void ConfigureServices(IServiceCollection services)
{
  //Added for session state
  services.AddDistributedMemoryCache();

  services.AddSession(options =>
  {
  options.IdleTimeout = TimeSpan.FromMinutes(10);               
  });
}

The simple method to store and read data from session is;

# In a class;
Session.SetString("Email", "foo.com"); //store data
Session.GetString("Email"); //read data

# In Razor pages
@using Microsoft.AspNetCore.Http; 
string CustomerEmail = String.Empty;
@if (Context.Session.GetString("Email") != null)
 {
     CustomerEmail = Context.Session.GetString("Email").ToString();
 }
}

# You can use it in Razor markup 
<ul class="navbar-nav mr-auto float-right">
   <li class="nav-item">
      <span class="navbar-text text-light">Hello @CustomerEmail</span>
   </li>

</ul>

In order to store complex objects in your session in .NET Core, follow the following steps:

Create a model class of your object type (in your case EmployeeDetails):

public class EmployeeDetails
{
    public string EmployeeId { get; set; }
    public string DesignationId { get; set; }
}

Then create a SessionExtension helper to set and retrieve your complex object as JSON:

public static class SessionExtensions
{
  public static void SetObjectAsJson(this ISession session, string key, object value)
   {
     session.SetString(key, JsonConvert.SerializeObject(value));
   }

   public static T GetObjectFromJson<T>(this ISession session, string key)
   {
     var value = session.GetString(key);
     return value == null ? default(T) : JsonConvert.DeserializeObject<T>(value);
   }
}

Then finally set the complex object in your session as:

var employee = new EmployeeDetails();
employee.EmployeeId = "1";
employee.DesignationId = "2";

HttpContext.Session.SetObjectAsJson("EmployeeDetails", employee);

To retrieve your complex object in your session:

var employeeDetails = HttpContext.Session.GetObjectFromJson<EmployeeDetails>("EmployeeDetails");
int employeeID = Convert.ToInt32(employeeDetails.EmployeeId);
int designationID= Convert.ToInt32(employeeDetails.DesignationId);

My session was not working. it turns out that it relates to GDPR issues. Three fixes;

FIX-I

The first fix is to provide user a login page and let him accept cookies policy.

If you don’t provide a login page and still want to configure sessions in ASP.NET Core, you need these two fixes in Startup.cs file;

Fix-II Startup.cs file ConfigureServices method. Add this line;

 services.AddSession(options =>
 {
    options.Cookie.IsEssential = true;
 });

Fix-III Startup.cs file Configure method, comment this line;

//app.UseCookiePolicy();

The most common fix is FIX-I. For testing I choose Fix-II and session started working.

Sources

https://andrewlock.net/session-state-gdpr-and-non-essential-cookies/