# 1. Start 'Hello world!'

# Set up the environment

## Download SDK

Download dotnet SDK here. %\[https://dotnet.microsoft.com/\]

You can check your SDK info on PowerShell by below command.

```csharp
dotnet --info
```

**Command output**

```bash
$ dotnet --info
.NET SDK:
 Version:   7.0.300-preview.23122.5
 Commit:    cc3d10e792

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.25357
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\7.0.300-preview.23122.5\

Host:
  Version:      7.0.3
  Architecture: x64
  Commit:       0a2bda10e8

.NET SDKs installed:
  6.0.202 [C:\Program Files\dotnet\sdk]
  6.0.203 [C:\Program Files\dotnet\sdk]
  6.0.301 [C:\Program Files\dotnet\sdk]
  6.0.404 [C:\Program Files\dotnet\sdk]
  7.0.100 [C:\Program Files\dotnet\sdk]
  7.0.300-preview.23122.5 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.App 6.0.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 6.0.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 6.0.12 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 6.0.14 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 7.0.3 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 6.0.4 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 6.0.5 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 6.0.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 6.0.12 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 6.0.14 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 7.0.3 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 6.0.4 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 6.0.5 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 6.0.6 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 6.0.12 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 6.0.14 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 7.0.3 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Other architectures found:
  x86   [C:\Program Files (x86)\dotnet]
    registered at [HKLM\SOFTWARE\dotnet\Setup\InstalledVersions\x86\InstallLocation]

Environment variables:
  Not set

global.json file:
  Not found

Learn more:
  https://aka.ms/dotnet/info

Download .NET:
  https://aka.ms/dotnet/download
```

# **Creating sample console app**

| option |  |
| --- | --- |
| \-o | Location of generated project |
| \-f | implicit framework |

```bash
$ dotnet new console -o HelloWorld -f net7.0
The template "Console App" was created successfully.

Processing post-creation actions...
Restoring C:\Users\archdsp\Projects\HelloWorld\HelloWorld.csproj:
  Determining projects to restore...
  Restored C:\Users\archdsp\Projects\HelloWorld\HelloWorld.csproj (in 97 ms).
Restore succeeded.
```

**Project directory**

```bash
Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
d-----         5/17/2023   1:46 PM                obj
-a----         5/17/2023   1:46 PM            249 HelloWorld.csproj
-a----         5/17/2023   1:46 PM            105 Program.cs
```

## Compile, Build, Executing

### with Roslyn compiler

#### Find compiler and add the path as Environment Variable

```bash
dir -Path C:\ -Filter csc.exe -Recurse -ErrorAction SilentlyContinuecsc
```

#### Compile

You can compile `Program.cs` with Roslyn compiler with command.

```bash
csc.exe Program.cs
```

This will generate Program.exe under project directory

```bash
Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
d-----         5/17/2023   1:54 PM                obj
-a----         5/17/2023   1:46 PM            249 HelloWorld.csproj
-a----         5/17/2023   1:54 PM            122 Program.cs
-a----         5/17/2023   1:55 PM           4096 Program.exe
```

> More option can be found with
> 
> ```bash
> csc.exe /help
> ```

### With dotnet build

```bash
dotnet build .\HelloWorld.csproj
```

This will generate output under bin\\ directory.

```bash
    Directory: C:\Users\archdsp\Projects\HelloWorld\bin\Debug\net7.0


Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
-a----         5/17/2023   2:04 PM            422 HelloWorld.deps.json
-a----         5/17/2023   2:03 PM           5120 HelloWorld.dll
-a----         5/17/2023   2:03 PM         154112 HelloWorld.exe
-a----         5/17/2023   2:03 PM          10516 HelloWorld.pdb
-a----         5/17/2023   2:04 PM            147 HelloWorld.runtimeconfig.json
```

### Difference

| Command | Target | On linux |
| --- | --- | --- |
| csc.exe | Source code | `GCC` or `Clang` |
| dotnet.exe build | .proj file | `Make` or `CMake` maybe... |

### Executing

```bash
dotnet run .\Program.cs
dotnet run .\Program.exe
dotnet run .\HelloWorld.csproj
dotnet .\bin\Debug\net7.0\HelloWorld.dll
```