Parsing error: Adjacent JSX elements must be wrapped in an enclosing tag. Did you want a JSX fragment <>...?

class App extends React.Component {

render() {

return (

<Header />

<Content/>

);

}

}

This code throw error as follow :

./src/App.js
  Line 9:  Parsing error: Adjacent JSX elements must be wrapped in an enclosing tag. Did you want a JSX fragment <>...</>?

   7 |     return (
   8 |     

>  9 |     
     |     ^
  10 |     );
  11 |   }
  12 | }

to solve that error that you need to put your component tags into elclosing tags

like this 




return (
    <div>
       <Comp1 />
       <Comp2 />
    </div>
)
or you can use the <React.Fragment>
return (
    <React.Fragment>
       <Comp1 />
       <Comp2 />
    </React.Fragment>
) 

https://reactjs.org/docs/fragments.html 

Error : verbose stack Error: ENOENT: no such file or directory, open 'Roaming\npm-cache\_npx\1768\package.json

When running npx (with any arguments, but -v is easiest to test) from the global install folder, the following error is produced.

The above error is due the white space contain in your username of PC. The command npx create-react-app doesn't work in this situation and shows error.

Solution : 

1. run npm config edit to edit your config
2. change cache path,e.g.
   from cache=D:\program file\npm-cache to cache=D:\progra~1\npm-cache

how-can-i-remove-duplicate-rows

;WITH cte
     AS (SELECT ROW_NUMBER() OVER (PARTITION BY Col1, Col2, Col3 
                                       ORDER BY ( SELECT 0)) RN
         FROM   #MyTable)
DELETE FROM cte
WHERE  RN > 1

nth max salary in sql

WITH CTE AS
(
    SELECT EmpID,EmpName,EmpSalar,
           RN = ROW_NUMBER() OVER (ORDER BY EmpSalary DESC)
    FROM dbo.Salary
)
SELECT EmpID,EmpName,EmpSalar
FROM CTE
WHERE RN = @NthRow

interface with same method name in c#

interface IPrinter
    {
        void print(string a);
    }

    interface IPrinter1
    {
        void print(string a);
    }




class Program
    {
        static void Main(string[] args)
        {
            IPrinter p = new Printer();
            p.print("rahul");

            Printer p1 = new Printer();
            ((IPrinter)p1).print("overlaoded");
        }
      
    }

    class Printer : IPrinter, IPrinter1
    {
         void IPrinter.print(string a)
        {
            Console.Write(a + "Printer");
            Console.ReadLine();
        }

         void IPrinter1.print(string a)
        {
            Console.Write(a+"Printer1");
            Console.ReadLine();
        }
    }

difference between save and insert in mongodb

If the document contains an _id field, then the save() method performs an upsert querying the collection on the _id field: If a document does not exist with the specified _id value, the save() method performs an insert with the specified fields in the document. If a document exists with the specified _id value, the save() method performs an update, replacing all field in the existing record with the fields from the document.

Child Actions in ASP.NET MVC

Child Actions are the action methods which can be invoked within the view. This is used to work with the data in the view, which are not related to the main action method. For example, if you want to create a data driven widget in the view using data that is not related to the main action method, you will need to use the child action method.
In ASP.NET MVC any action can be used as a child action. However, to use an action only as a child action and attribute it with the ChildActionOnly. It will make sure the action is not called by any user request and will only be used in the view. A child action can be created as shown below:

[ChildActionOnly] public ActionResult CurrentTime() { return PartialView(DateTime.Now); }

1 2 3 4 5

[ChildActionOnly]         public ActionResult CurrentTime()         {             return PartialView(DateTime.Now);         }

This child action returns a partial view with the current time as the data in the partial view. The partial view is created as below:
CurrentTime.cshtml

@model DateTime <p> Current time : @Model.ToShortTimeString() </p>

1 2 3

@model DateTime   <p>Current time : @Model.ToShortTimeString()   </p>

In the main view, the child action can be used as shown below:

@Html.Action("CurrentTime");

1	@Html.Action("CurrentTime");

Above we are using child action from the same controller in which the main action is defined. To use child actions from a different controller, you have the option of passing the controller name as well. You can also pass input parameters to the child action. To demonstrate this, let us create the child action with an input parameter as follows:

[ChildActionOnly] public ActionResult CurrentTime(object name) { return PartialView(name); }

1 2 3 4 5

[ChildActionOnly]         public ActionResult CurrentTime(object name)         {             return PartialView(name);         }

In the view, a parameter can be passed to the child action as follow:

@Html.Action("CurrentTime", new { name = "Steve" });

1	@Html.Action("CurrentTime", new { name = "Steve" });

You may consider using the child action method in the following scenarios,

• To use data in the view which is not related to the main controller
• To create data driven widgets to be used on different views