c# In multilevel inheritance, from child call parent class method by base keyword then observe behaviour

How to Integrate Swagger in .NetCore Web API project

Aim: Integrate Swagger in .NetCore Web API project

 (Visual Studio 2022 +  .NET 6)

 

1: Create new Web API project (without swagger built in integration)

We are not using OpenAPI in built from Demo.

We do all manually for better understanding

2: Install NuGet Package: SwashbuvkleAspNetCore

3: Update Program.cs file

    Builder.Services.AddSwaggerGen();

4:    Register Middleware

app.UseSwagger();

app.UseSwaggerUI()

 

To load swagger when we run project/ when we run project, landing page is swagger, 
need to update launchsetting.json file.

- set launchUrl to "swagger"

For step by step detail, watch video.

In LinkedIn profile section, How to add Stackoverflow profile

C# Custom Data Data Annotation - Validators with Example

 (1) What is Custom Data Annotations in C# model class? 

       When Custom Data Annotation useful? 

Ans : You have learn and regular and basic Data Annotation for validaion.

We  can apply validation at Model (POCO) class by using appropriate attribute.

Like Required, StringLength, MaxLength, EmailAddress and many more.

Now add following code for UI side

@model WebAppCustomDataAnnotation.Models.Student
<h2>Create</h2>

@using (Html.BeginForm()) 
{    
    <div class="form-horizontal">
        @Html.ValidationSummary(true, "", new { @class = "text-danger" })
        <div class="form-group">
            @Html.LabelFor(model => model.Name, htmlAttributes: new { @class = "control-label col-md-2" })
            @Html.EditorFor(model => model.Name, new { htmlAttributes = new { @class = "form-control" } })
            @Html.ValidationMessageFor(model => model.Name, "", new { @class = "text-danger" })
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.Email, htmlAttributes: new { @class = "control-label col-md-2" })
            @Html.EditorFor(model => model.Email, new { htmlAttributes = new { @class = "form-control" } })
            @Html.ValidationMessageFor(model => model.Email, "", new { @class = "text-danger" })
        </div>

        <div class="form-group">
            <input type="submit" value="Create" class="btn btn-default" />
        </div>
    </div>
}


@section Scripts {
    @Scripts.Render("~/bundles/jqueryval")
}

In this post we focus on custom Data Annotation.

When default attribute not sufficient to achieve our validation.
When validation is not achievable by Microsoft provided attribute 

For example - We have a Student table in Data base.

Before saving record, We need to check EMail value must be unique. 
But this is not achievable my available basic attribute.
But to tackle this limitation, we have Custom Data Annotation.
Assume system already contain email - "name@company.com"
If user try to insert same value again then validation must be there.
and error message will be prompt.
Create new class : 
UniqueEmailAttribute and inherit ValidationAttribute.
    
public class UniqueEmailAttribute : ValidationAttribute
    {

        protected override ValidationResult IsValid(object _value, ValidationContext validationContext)
        {

            if (_value != null && _value.ToString() == "name@company.com")
            {
                return new ValidationResult(ErrorMessage = "Email address already exist");
            }

            return ValidationResult.Success;
        }
    }
    


Here we have create Custom Data Annotation. 
It contain IsValid() method.
We have override this method and added logic to check existing value.

Provided Email value come at first parameter : object _value

If input email value is "name@company.com" then
it will return Error message.

Otherwise will return Success.(Validation passed)

You can provide error message as per your requirement.

This Method return ValidationResult.

Final Step :
Now add this created custom data annotation as attribute 
at Email property in Student class.
[Required(ErrorMessage = "Email address is required.")]
[UniqueEmail]
public string Email { get; set; }


Here error message is hard coded. but in real scenario it never happen.
So error message must be dynamicaly need to set.
In Student model - along with custom attribute "UniqueEmail", 
need to add ErrorMessage as shown in bellow.


As Error message set in Attribute, will show in bellow display 
when in Email field value added and "Create" button clicked as shown bellow.

SQL interview question Part-2

 Note :  All sql related question related to SQL Server.

(1) In SQL : How to swap column values​​ ?

Ans : 
update #tempSwap set EMPNAME = DEPT,DEPT = EMPNAME;

SQL interview question Part-1

Note :  All sql related question related to SQL Server.

(1) How to get current Age based on BirthDate ?

SELECT top 5 BirthDate,  DATEDIFF ( YEAR ,BirthDate , getdate() )  as age,LoginID

  FROM [HumanResources].[Employee]

(2)  What is the output when you concate two null value using plus '+'  operator ?

        SELECT NULL +  NULL;

Ans : It will resturn single null value.

(3)  What is the output when you concate two null value using CONCATE function ?

        SELECT CONCAT (NULL, NULL)

Ans : It will resturn empty string/ blank value.

(4)  What is the output of the following code ?

        

DECLARE @TempVariable AS NVARCHAR(50)

SET @TempVariable = 'Hello World'

PRINT @TempVariable

Ans : "Hello World"

(5)  What is the output of the following code ?

DECLARE @TempVariable AS NVARCHAR(50)

SET @TempVariable = 'Hello World'

GO

PRINT @TempVariable

Ans : It will gices error. - Must declare the scalar variable "@PurchaseName".

Reason is local variable scope expires at the end of the batch once "Go" statement came.

(6)  Teacher table have 6 records, contain LastName valiues as shown in bellow.

 What is the output of the following code ?

declare @tempLastName nvarchar(50);

select @tempLastName = LastName from [EF_Demo_DB].[dbo].Teacher;

select @tempLastName;

Ans : Jena

Explanation : Value of LastName from last record will be set in local variable @tempLastName.

(7)  What is output of following code snipet.

print null;

Ans : Blank 

Explanation : We cant print null value in sql server.

(8)  What is output of following code snipet.

Declare @localvariable nvarChar(50) =  NULL;

PRINT @localvariable + 'Tech for Boost';

Ans : Blank 

Explanation : concate with null value return blank value.

(9)  What is output of following code snipet.

declare @localvariable nvarchar(50) =  NULL;

PRINT 'Tech for Boost' + @localvariable;

Ans : Blank 

Explanation : concate with null value return blank value.

Null value containted variable in concation using '+' operator is first or second pposition does not matter.

but concation of null value using CONCAT function gives different result. Let's see with example.

(10)  What is output of following code snipet.

declare @localvariable nvarchar(50) =  NULL;

print CONCAT('Tech for Boost', @localvariable);

-- or

print CONCAT(@localvariable, 'Tech for Boost');

Ans : Tech for Boost

(11)  Can we use GROUP BY clause without aggregate function ?

Ans : Yes, let's see with example. We have table EmployeeSalary

How to Withdraw LinkedIn sent connection request?

C# interview question Part-1

0) What will be output of following c# code  ? (base class understanding)

(1) C# default access modifier

namespace :    public        

enum        :    public

interface :    public

class     :   private

struct           :   private

delegate         :   private  

constructor      :   private (note if no constructor is explicitly defined, 
                            a public default constructor will be automatically defined)
    
method           :   private

field            :   private

enum member      :  public

cinterface member: public

For example

namespace AccessDemo
{
    class OuterClass
    {
        void MethodA() {}
        class InnerClass {}
    }
}


is equivalent to
namespace AccessDemo
{
    internal class OuterClass
    {
        private void MethodA() {}
        private class InnerClass  {}
    }
}

(2)In Console Application, how to get input from the user ?
Ans : Using Console.ReadLine()
Console.Write("Enter input : ");
string userinput = Console.ReadLine();
Console.WriteLine("You entered '{0}'", userinput
);
output :
Enter input : test input
You entered 'test input'
'