let name: string;
name = "Vahid"; // OK
name = null; // OK
name = undefined;  // OK

let age: number;
age = 24; // OK
age = null; // OK
age = undefined;  // OK

{
    "compilerOptions": {
        "strictNullChecks": true
    }
}

 let foo: string = null; // Error! Type 'null' is not assignable to type 'string'.

Uncaught ReferenceError: foo is not defined
Uncaught TypeError: window.foo is not a function

// With strictNullChecks set to false
let d: Array<number> = [null, undefined, 10, 15]; //OK
let e: Array<string> = ["pie", null, ""];  //OK
 
 
// With strictNullChecks set to true
let d: Array<number> = [null, undefined, 10, 15]; // Error
let e: Array<string> = ["pie", null, ""]; // Error

{ 
    "compilerOptions": { 
        "strict": true  /* Enable all strict type-checking options. */ 
    } 
}

{ 
    "compilerOptions": { 
        "strict": true, 
        "noImplicitThis": false 
    } 
}

 let foo: string | null = null; // Okay!

let name: string | null;
name = "Vahid"; // OK
name = null; // OK
name = undefined;  // Error

let z = null;

testAssignedBeforeUseChecking() {
    let x: number;
    console.log(x);
}

 [ts] Variable 'x' is used before being assigned.

let z: number | undefined;
console.log(z);

method1(x?: number) {
}

method1(x?: number | undefined) {
}

  f(x: number): string {
    return x.toString();
  }

  testTypeGuards() {
    let x: number | null | undefined;
    if (x) {
      this.f(x);  // Ok, type of x is number here
    } else {
      this.f(x);  // Error, type of x is number? here
    }
  }

 Argument of type 'number | null | undefined' is not assignable to parameter of type 'number'.
Type 'undefined' is not assignable to type 'number'.

getLength(s: string | null) {
   return s ? s.length : 0;
}

isNumber(n: any): n is number { // type guard
   return typeof n === "number";
}

  usedMb(usedBytes?: number): number | undefined {
    return this.isNumber(usedBytes) ? (usedBytes / (1024 * 1024)) : undefined;
  }

  usedMb2(usedBytes?: number): number | undefined {
    return usedBytes ? (usedBytes / (1024 * 1024)) : undefined;
  }

  formatUsedMb(): string {
    //ERROR: TS2531: Object is possibly undefined
    return this.usedMb(123).toFixed(0).toString();
  }

  formatUsed(): string {
    const usedMb = this.usedMb(123);
    return usedMb ? usedMb.toFixed(0).toString() : "";
  }

export interface User {
  name: string;
  age?: number;
}

  printUserInfo(user: User) {
    if (user.age != null) {
      console.log(`${user.name}, ${user.age.toString()}`);
    }
  }

  printUserInfo(user: User) {
    console.log(`${user.name}, ${user.age.toString()}`);
  }

  printUserInfo(user: User) {
    console.log(`${user.name}, ${user.age!.toString()}`);
  }

 [tslint] Forbidden non null assertion (no-non-null-assertion)

 Create Table <name> (…) ON …

 Where [OrderDate] Between …

USE [PartitionDB]
GO
CREATE PARTITION FUNCTION pfOrderDateRange(DATETIME)
AS
RANGE LEFT FOR VALUES ('2010/12/31','2011/12/31','2012/12/31')
GO
CREATE PARTITION SCHEME psOrderDateRange
AS
PARTITION pfOrderDateRange TO (FG1,FG2,FG3,[PRIMARY])
GO

CREATE TABLE Orders
(
OrderID INT IDENTITY(1,1) NOT NULL,
OrderDate DATETIME NOT NULL,
OrderFreight MONEY NULL,
ProductID INT NULL,
CONSTRAINT PK_Orders PRIMARY KEY CLUSTERED (OrderID ASC, OrderDate ASC)
ON psOrderDateRange (OrderDate)
) ON psOrderDateRange (OrderDate)
GO

SET NOCOUNT ON
DECLARE @OrderDate DATETIME
DECLARE @X INT
SET @OrderDate = '2010/01/01'
SET @X = 0
WHILE @X < 300
BEGIN
INSERT dbo.Orders ( OrderDate, OrderFreight, ProductID)
VALUES( @OrderDate + @X, @X + 10, @X)
 SET @X = @X + 1
END
GO
SET NOCOUNT ON
DECLARE @OrderDate DATETIME
DECLARE @X INT
SET @OrderDate = '2011/01/01'
SET @X = 0
WHILE @X < 300
BEGIN
INSERT dbo.Orders ( OrderDate, OrderFreight, ProductID)
VALUES( @OrderDate + @X, @X + 10, @X)
 SET @X = @X + 1
END
GO
SET NOCOUNT ON
DECLARE @OrderDate DATETIME
DECLARE @X INT
SET @OrderDate = '2012/01/01'
SET @X = 0
WHILE @X < 300
BEGIN
INSERT dbo.Orders ( OrderDate, OrderFreight, ProductID)
VALUES( @OrderDate + @X, @X + 10, @X)
 SET @X = @X + 1
END
GO

USE [PartitionDB]
GO
SELECT OBJECT_NAME(i.object_id) AS OBJECT_NAME,
p.partition_number, fg.NAME AS FILEGROUP_NAME, ROWS, au.total_pages,
CASE boundary_value_on_right
WHEN 1 THEN 'Less than'
ELSE 'Less or equal than' END AS 'Comparition',VALUE
FROM sys.partitions p JOIN sys.indexes i
ON p.object_id = i.object_id AND p.index_id = i.index_id
JOIN sys.partition_schemes ps ON ps.data_space_id = i.data_space_id
JOIN sys.partition_functions f ON f.function_id = ps.function_id
LEFT JOIN sys.partition_range_values rv
ON f.function_id = rv.function_id
AND p.partition_number = rv.boundary_id
JOIN sys.destination_data_spaces dds
ON dds.partition_scheme_id = ps.data_space_id
AND dds.destination_id = p.partition_number
JOIN sys.filegroups fg
ON dds.data_space_id = fg.data_space_id
JOIN (SELECT container_id, SUM(total_pages) AS total_pages
FROM sys.allocation_units
GROUP BY container_id) AS au
ON au.container_id = p.partition_id WHERE i.index_id < 2

/* Query 2-3- Split a partition*/
-- Add FG4:
ALTER DATABASE PartitionDB ADD FILEGROUP FG4
Go
ALTER PARTITION SCHEME [psOrderDateRange] NEXT USED FG4
GO
ALTER PARTITION FUNCTION [pfOrderDateRange]() SPLIT RANGE('2013/12/31')
GO
-- Add Partition 4 (P4) to FG4:
GO
ALTER DATABASE PartitionDB ADD FILE
(
NAME = P4,
FILENAME = N'C:\Program Files\Microsoft SQL Server\MSSQL10_50.SQLEXPRESS\MSSQL\DATA\P4.NDF'
, SIZE = 1024KB , MAXSIZE = UNLIMITED, FILEGROWTH = 10%)
 TO FILEGROUP [FG4]
--
GO

SET NOCOUNT ON
DECLARE @OrderDate DATETIME
DECLARE @X INT
SET @OrderDate = '2013/01/01'
SET @X = 0
WHILE @X < 300
BEGIN
INSERT dbo.Orders ( OrderDate, OrderFreight, ProductID)
VALUES( @OrderDate + @X, @X + 10, @X)
 SET @X = @X + 1
END
GO
SET NOCOUNT ON
DECLARE @OrderDate DATETIME
DECLARE @X INT
SET @OrderDate = '2012/01/01'
SET @X = 0
WHILE @X < 300
BEGIN
INSERT dbo.Orders ( OrderDate, OrderFreight, ProductID)
VALUES( @OrderDate + @X, @X + 10, @X)
 SET @X = @X + 1
END
GO

/* Query 2-4- Merge Partitions */
ALTER PARTITION FUNCTION [pfOrderDateRange]() MERGE RANGE('2010/12/31')
Go

/* Query 2-5- Switch Partitions */
USE [PartitionDB]
GO
CREATE TABLE [dbo].[Orders_Temp](
[OrderID] [int] IDENTITY(1,1) NOT NULL,
[OrderDate] [datetime] NOT NULL,
[OrderFreight] [money] NULL,
[ProductID] [int] NULL,
 CONSTRAINT [PK_OrdersTemp] PRIMARY KEY CLUSTERED ([OrderID] ASC,[OrderDate] ASC)ON FG2
) ON FG2
GO
USE [tempdb]
GO
CREATE TABLE [dbo].[Orders_Hist](
[OrderID] [int] NOT NULL,
[OrderDate] [datetime] NOT NULL,
[OrderFreight] [money] NULL,
[ProductID] [int] NULL,
 CONSTRAINT [PK_OrdersTemp] PRIMARY KEY CLUSTERED ([OrderID] ASC,[OrderDate] ASC)
)
GO
USE [PartitionDB]
GO
ALTER TABLE [dbo].[Orders] SWITCH PARTITION 1 TO [dbo].[Orders_Temp]
GO
INSERT INTO [tempdb].[dbo].[Orders_Hist]
SELECT * FROM  [dbo].[Orders_Temp]
GO
DROP TABLE [dbo].[Orders_Temp]
GO
SELECT * FROM [tempdb].[dbo].[Orders_Hist]

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Microsoft Build 2021
Explore what’s next in tech and the future of hybrid work. Join us May 25–27, 2021 at Microsoft Build.
 

Jon Skeet presents some of the features coming in C# 7 - tuples, pattern matching, local functions, throw expressions, numeric literals, and more – along with hints regarding future versions.  

OWASP dependency-check is a software composition analysis utility that detects publicly disclosed vulnerabilities in application dependencies.  

we extract language rankings from GitHub and Stack Overflow, and combine them for a ranking that attempts to reflect both code (GitHub) and discussion (Stack Overflow) traction. The idea is not to offer a statistically valid representation of current usage, but rather to correlate language discussion and usage in an effort to extract insights into potential future adoption trends.