How to stream image from generic handler

This article provides an example of streaming images from a generic handler in .NET.

If you store your images in a database table as byte[] then you can utilize a handler to display them in a data grid.

The process involves sending a request to the handler (.ashx) page, retrieving the image, and then displaying it.

In the given example, we have a grid that stores IDs in one column and displays the corresponding images in another column using an asp:ImageField.

Create a generic handler that streams image. In this example ImageField requests image from getFaceImage.ashx by DataImageUrlField parameter in DataImageUrlFormatString format

public void ProcessRequest(HttpContext context)
{
    int id;

    if (context.Request.QueryString["id"] != null)
    {
        id = Convert.ToInt32(context.Request.QueryString["id"]);

        if (id > 0)
        {
            context.Response.ContentType = "image/jpeg";

            Stream strm = new MemoryStream();
            GetImage(id).Save(strm, ImageFormat.Jpeg);
            strm.Position = 0;

            byte[] buffer = new byte[4096];
            int byteSeq = strm.Read(buffer, 0, 4096);
            while (byteSeq > 0)
            {
                context.Response.OutputStream.Write(buffer, 0, byteSeq);
                byteSeq = strm.Read(buffer, 0, 4096);
            }
        }
    }
    else
        return;
}

public Image GetImage(int id)
{
    //Make appropriate calls for image according to id
    //...

    //return the image
    return new Bitmap("");
}

Read More

[Tips] Random string generators C#

Testing 2 different Random string generators.

void Main()
{
 for(int i=0;i<10;i++){
  Console.WriteLine("GetRandomString: " + GetRandomString(8));
 }
 for(int i=0;i<10;i++){
  Console.WriteLine("GetRandomFileName: " + GetRandomFileName());
 } 
}

public static string GetRandomString(int length)
{
    Random random = new Random();
    const string chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
    return new string(Enumerable.Repeat(chars, length)
      .Select(s => s[random.Next(s.Length)]).ToArray());
}

public static string GetRandomFileName()
{
    string path = Path.GetRandomFileName();
    path = path.Replace(".", ""); // Remove period.
    return path;
}

Result

GetRandomString: tpZIDi0C
GetRandomString: tpZIDi0C
GetRandomString: tpZIDi0C
GetRandomString: tpZIDi0C
GetRandomString: tpZIDi0C
GetRandomString: tpZIDi0C
GetRandomString: tpZIDi0C
GetRandomString: tpZIDi0C
GetRandomString: tpZIDi0C
GetRandomString: tpZIDi0C
GetRandomFileName: smb1u03pvyf
GetRandomFileName: 2ccre5kihis
GetRandomFileName: 24thz5is1pj
GetRandomFileName: ni0z42lexag
GetRandomFileName: 1u11tcvd3qv
GetRandomFileName: vtiqp2sevwy
GetRandomFileName: y2jhumy1hcx
GetRandomFileName: 5o0gsyronpk
GetRandomFileName: m0zva3mhdfn
GetRandomFileName: 2a2dzcdkpbl

Read More

Dynamic Assembly Loading (C# Reflection)

We will achieve following task with dynamic assembly loading in C#.

using System.Net.Http;
using System;
using System.Linq;

var client = new HttpClient();
client.BaseAddress = new Uri("http://api.open-notify.org/astros.json");
string result = client.GetStringAsync("").Result;

Don't add System.Net.Http dll to your reference list. It will be automatically loaded from GAC.

using System;
using System.Linq;
using System.Reflection;

//We don't have "using System.Net.Http" 

//Load System.Net.Http
string name1 = "System.Net.Http,Version=4.0.0.0," + "Culture=neutral,PublicKeyToken=b03f5f7f11d50a3a";
Assembly a1 = Assembly.Load(name1);

//Create HttpClient instance
Type clientType = a1.GetTypes().Where(t => t.Name.Equals("HttpClient")).Single();
object client = Activator.CreateInstance(clientType);

//Set BaseAddress on client
PropertyInfo propertyBaseAddress = clientType.GetProperties().Where(p => p.Name == "BaseAddress").Single();
Uri url = new Uri("http://api.open-notify.org/astros.json");
propertyBaseAddress.SetValue(client, url);

//Test property value
var BaseAddressValue = propertyBaseAddress.GetValue(client);

//Get HttpResponseMessage Task
var methodGetStringAsync = clientType.GetMethod("GetStringAsync", new Type[] { typeof(Uri) });
var responseTask = methodGetStringAsync.Invoke(client, new string[] { null });

//Get HttpResponseMessage result from Task
var responseType = responseTask.GetType();
PropertyInfo propResponse = responseType.GetProperties().Where(p => p.Name == "Result").Single();

var responseResult = propResponse.GetValue(responseTask);  //This is the string result

Bonus: List your loaded assemblies

Assembly[] assemblies = AppDomain.CurrentDomain.GetAssemblies();

foreach (Assembly a in assemblies)
{
     Console.WriteLine(a.GetName());
}

Output

mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089 System.Core, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089 System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089 System.Net.Http, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a System.Configuration, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a System.Xml, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089

System.Net.Http is displayed here even not referenced in Visual Studio.

Read More

Upload file to Console Webapi (Owin)

Upload a file to a console based webapi host (owin).

Method 1: MultipartFormDataStreamProvider

 

[HttpPost]
public async Task PostFile()
{
 string root = AppDomain.CurrentDomain.BaseDirectory + "Uploads"; 

 var provider = new MultipartFormDataStreamProvider(root);
 await Request.Content.ReadAsMultipartAsync(provider);
 foreach (var file in provider.FileData)
 {
  var buffer = File.ReadAllBytes(file.LocalFileName);  
 }
 return new HttpResponseMessage() { Content = new StringContent("OK") };
}

Postman Post Sample

Select form-data for Body. Enter key name and select a file for the value.

POST /api/file/PostByteArrayAsync HTTP/1.1
Host: 127.0.0.1:5000
Content-Type: multipart/form-data; boundary=----WebKitFormBoundary7MA4YWxkTrZu0gW
Content-Length: 15143
Connection: keep-alive
cache-control: no-cache


Content-Disposition: form-data; name="file"; filename="/C:/Users/oktay/logs.txt


------WebKitFormBoundary7MA4YWxkTrZu0gW--

Method 2: ReadAsByteArrayAsync

This method requires filename in header. Add key/value for "filename".

 

[HttpPost]
public string PostFile()
{
 string fileName = Request.Headers.GetValues("filename").ElementAt(0);

 string root = AppDomain.CurrentDomain.BaseDirectory + "Uploads\\";
 var filePath = root + fileName;

 var fc = Request.Content.ReadAsByteArrayAsync().Result;
 File.WriteAllBytes(filePath, fc);

 return "uploaded";
}

Read More

Decryption function (dotnet & nodejs)

In "Encryption function (dotnet & nodejs)" post I described encryption functions.
In this post you can see decrypt functions.

Nodejs uses "crypto-js" package.
Dotnet uses "System.Security.Cryptography" namespace.

Dotnet

 

public static string Decrypt(string encryptedBase64)
{
 byte[] rawSecretKey = { 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01 };  
 string PassPhrase = "passPhrase";

 MD5CryptoServiceProvider x = new System.Security.Cryptography.MD5CryptoServiceProvider();
 byte[] data = Encoding.ASCII.GetBytes(PassPhrase);
 data.Dump("data");
 
 byte[] passwordKey = x.ComputeHash(data);
 
 RijndaelManaged rijndael = new RijndaelManaged();
 ICryptoTransform rijndaelDecryptor = rijndael.CreateDecryptor(passwordKey, rawSecretKey);
 try
 {
  byte[] encryptedData = Convert.FromBase64String(encryptedBase64);
  byte[] newClearData = rijndaelDecryptor.TransformFinalBlock(encryptedData, 0, encryptedData.Length);
  return Encoding.ASCII.GetString(newClearData);
 }
 catch (Exception ex)
 {
  return null;
 }
}

Node.js

 

 var bytes = CryptoJS.AES.decrypt(encrypted, myRijndaelKey, {
        iv: ivCodeWords,
        mode: CryptoJS.mode.CBC,
        padding: CryptoJS.pad.Pkcs7
    });
 var plaintext = bytes.toString(CryptoJS.enc.Utf8);
 console.log("decrypted text: " + plaintext);

Read More

Web Api Post Types (C#)

You can find some implementations of Web Api Post types here.

Model

public class Model
{
 public string Name { get; set; }
 public string Id { get; set; }

 public string Save()
 {
  return "Saved";
 }
}

1. Post Raw

Web Api

[HttpPost]
public async Task PostRaw()
{
 string json = await Request.Content.ReadAsStringAsync();

 Model model = Newtonsoft.Json.JsonConvert.DeserializeObject(json);

 return model.Save();
}

Request

POST http://localhost:63693/api/test/PostRaw HTTP/1.1
Content-Type: application/json

{"Id":"1","Name":"Model1"}

2. FromBody

Web Api

[HttpPost]
public string PostFromBody([FromBody]string body)
{
 Model model = Newtonsoft.Json.JsonConvert.DeserializeObject(body);

 return model.Save();
}

Request

Escape json: "{\"Id\":\"1\",\"Name\":\"Model1\"}"

POST http://localhost:63693/api/test/PostModel HTTP/1.1
Content-Type: application/json

"{\"Id\":\"1\",\"Name\":\"Model1\"}"

or

POST http://localhost:63693/api/test/PostFromBody HTTP/1.1
Content-Type: application/x-www-form-urlencoded

%7B%22body%22=%7B%22Id%22%3A%221%22%2C%22Name%22%3A%22Model1%22%7D%7D

3. Class parameter

Web Api

[HttpPost]
public string PostModel(Model model)
{
 return model.Save();
}

Request

POST http://localhost:63693/api/test/PostModel HTTP/1.1
Content-Type: application/json

{"Id":"1","Name":"Model1"}

4. String parameter + Request.Content

Web Api

[HttpPost]
public string PostModelJson(string key)
{
 //You may check key here...

 var contentType = Request.Content.Headers.ContentType.MediaType;
 var body = Request.Content.ReadAsStringAsync().Result;

 Model model = null;

 if (contentType == "application/json")
 {
  model = Newtonsoft.Json.JsonConvert.DeserializeObject(body);

  return model.Save();
 }
 else
  throw new HttpResponseException(HttpStatusCode.UnsupportedMediaType);
}

Request

POST http://localhost:63693/api/test/PostModelJson?key=1 HTTP/1.1
Content-Type: application/json

{"Id":"1","Name":"Model1"}

5. Post uri parameter

Web Api

[HttpPost]
public string PostModelFromUri([FromUri]Model model)
{
 return model.Save();
}

Request

POST http://localhost:63693/api/test/PostModelFromUri?id=1&name=Model1 HTTP/1.1

6. Multipart Form Data

Web Api

[HttpPost]
public string PostMultipart()
{
 var contentType = Request.Content.Headers.ContentType.MediaType;

 if (contentType == "multipart/form-data")
 {
  var parts = Request.Content.ReadAsMultipartAsync().Result;

  var contents = parts.Contents;
  Model model = new Model();

  foreach (StreamContent item in contents)
  {
   if (item.Headers.ContentDisposition.Name.Trim('"') == "Id")
    model.Id = item.ReadAsStringAsync().Result;
   else if (item.Headers.ContentDisposition.Name.Trim('"') == "Name")
    model.Name = item.ReadAsStringAsync().Result;
  }

  return model.Save();
 }
 else
  throw new HttpResponseException(HttpStatusCode.UnsupportedMediaType);            
}

Request

POST http://localhost:63693/api/test/PostMultipart HTTP/1.1
Content-Type: multipart/form-data; boundary=----WebKitFormBoundaryrKvJKnAHtuVvEERM

------WebKitFormBoundaryrKvJKnAHtuVvEERM
Content-Disposition: form-data; name="Id"

1
------WebKitFormBoundaryrKvJKnAHtuVvEERM
Content-Disposition: form-data; name="Name"

Model1
------WebKitFormBoundaryrKvJKnAHtuVvEERM--

Read More

Encryption function (dotnet & nodejs)

Following functions give same result on dotnet and nodejs platforms.
Nodejs uses "crypto-js" package.
Dotnet uses "System.Security.Cryptography" namespace.

Dotnet

void Main()  
 {  
     string clearText = "oktay";  
     Console.WriteLine("clearText: " + clearText);  
     string encrypted = Crypto.EncryptToBase64(clearText);  
     Console.WriteLine("encrypted: " + encrypted);  
 }  
 public static class Crypto  
 {  
   public static string EncryptToBase64(string decryptedText)  
   {  
     byte[] rawSecretKey = { 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01 };  
     string PassPhrase = "passPhrase";  
     MD5CryptoServiceProvider x = new System.Security.Cryptography.MD5CryptoServiceProvider();  
     byte[] data = Encoding.UTF8.GetBytes(PassPhrase);  
         byte[] passwordKey = x.ComputeHash(data);  
         Console.WriteLine("key: " + BitConverter.ToString(passwordKey).Replace("-", ""));  
         Console.WriteLine("iv : " + BitConverter.ToString(rawSecretKey).Replace("-", ""));  
         RijndaelManaged rijndael = new RijndaelManaged();  
     ICryptoTransform rijndaelEncryptor = rijndael.CreateEncryptor(passwordKey, rawSecretKey);  
     try  
     {  
       byte[] decryptedData = Encoding.UTF8.GetBytes(decryptedText);  
       byte[] newClearData = rijndaelEncryptor.TransformFinalBlock(decryptedData, 0, decryptedData.Length);  
       return Convert.ToBase64String(newClearData, 0, newClearData.Length);  
     }  
     catch (Exception ex)  
     {  
       throw ex;  
     }  
   }  
 }  

Node.js

 
 var CryptoJS = require("crypto-js");  
 function byteArrayToHexString(byteArray) {  
  return Array.prototype.map  
   .call(byteArray, function(byte) {  
    return ("0" + (byte & 0xff).toString(16)).slice(-2);  
   })  
   .join("");  
 }  

 function EncryptToBase64(password) {
  console.log("clearText: " + password); 
  var PassPhrase = "passPhrase";  
  var rawSecretKey = [ 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01 ];
  
  var myRijndaelKeyBytes = CryptoJS.enc.Utf8.parse(PassPhrase);  
  var myRijndaelKey = CryptoJS.MD5(CryptoJS.enc.Utf8.parse(PassPhrase));  
  console.log("key: " + myRijndaelKey);  
  var myRijndaelIV = byteArrayToHexString(rawSecretKey);  
  var ivCodeWords = CryptoJS.enc.Hex.parse(myRijndaelIV);  
  console.log("iv: " + ivCodeWords);  
  var encrypted = CryptoJS.AES.encrypt(  
   CryptoJS.enc.Utf8.parse(password),  
   myRijndaelKey,  
   {  
    iv: ivCodeWords,  
    mode: CryptoJS.mode.CBC,  
    padding: CryptoJS.pad.Pkcs7  
   }  
  );  
  var base64 = CryptoJS.enc.Base64.stringify(encrypted.ciphertext);  
  console.log("encrypted: " + base64);  
 }  
 EncryptToBase64("oktay");  
 return;  

Result

clearText: oktay
key: C6CEC8C6CAA9A579644664F0575DB2F5
iv : 01010101010101010101010101010101
encrypted: S+6CSoMM6no9atihmfyayQ==

Read More

Query samples on a self referenced table (Part-4)

In previous post we joined tables but there was a problem. We can not see "Help" menu which has not any sub menu. To solve the problem we will use Outer Join.

Linq

var menus = from t in Menus
  where t.MenuType==1
  join s in Menus on t.MenuID equals s.MenuParent into Subs
  from ss in Subs.DefaultIfEmpty()
  select new {
   TopMenu = t.Title,
   SubMenu = ss == null ? null : ss.Title
  };

Lambda

Menus
   .Where (t => (t.MenuType == 1))
   .GroupJoin (
      Menus, 
      t => (t.MenuID), 
      s => s.MenuParent, 
      (t, Subs) => 
         new  
         {
            t = t, 
            Subs = Subs
         }
   )
   .SelectMany (
      temp0 => temp0.Subs.DefaultIfEmpty (), 
      (temp0, ss) => 
         new  
         {
            TopMenu = temp0.t.Title, 
            SubMenu = (ss == null) ? null : ss.Title
         }
   )

SQL

DECLARE @p0 Int = 1

SELECT [t0].[Title] AS [TopMenu], 
    (CASE 
        WHEN [t2].[test] IS NULL THEN NULL
        ELSE CONVERT(NVarChar(MAX),[t2].[Title])
     END) AS [SubMenu]
FROM [Menu] AS [t0]
LEFT OUTER JOIN (
    SELECT 1 AS [test], [t1].[Title], [t1].[MenuParent]
    FROM [Menu] AS [t1]
    ) AS [t2] ON ([t0].[MenuID]) = [t2].[MenuParent]
WHERE [t0].[MenuType] = @p0

Read More

Query samples on a self referenced table (Part-3)

In previous post we queried tables.

In this post we will join the tables. This will show Top Menu title and Sub Menu title in a row.

Linq

var menus = from t in Menus
  where t.MenuType == 1
  join s in Menus on t.MenuID equals s.MenuParent
  select new {
   TopMenu = t.Title,
   SubMenu = s.Title
  };

Lambda

Menus
   .Where (t => (t.MenuType == 1))
   .Join (
      Menus, 
      t => (Int32?)(t.MenuID), 
      s => s.MenuParent, 
      (t, s) => 
         new  
         {
            TopMenu = t.Title, 
            SubMenu = s.Title
         }
   )

SQL

DECLARE @p0 Int = 1

SELECT [t0].[Title] AS [TopMenu], [t1].[Title] AS [SubMenu]
FROM [Menu] AS [t0]
INNER JOIN [Menu] AS [t1] ON ([t0].[MenuID]) = [t1].[MenuParent]
WHERE [t0].[MenuType] = @p0

Read More

Query samples on a self referenced table (Part-2)

In previous post we created a database table, filled it with sample data and saw some basic queries.

In this post we will query the table in { Menu.Title, IEnumerable<menu> } form. This will show Top menu title and sub menu items in a row.

Linq

var menus = from t in Menus 
 where t.MenuType==1 
 select new {
  t.Title,
  SubMenus = from s in Menus
  where t.MenuType==1 && t.MenuID==s.MenuParent
  select s
 };

Lambda

Menus
   .Where (t => (t.MenuType == 1))
   .Select (
      t => 
         new  
         {
            Title = t.Title, 
            SubMenus = Menus
               .Where (s => ((t.MenuType == 1) && ((Int32?)(t.MenuID) == s.MenuParent)))
         }
   )

SQL

DECLARE @p0 Int = 1
DECLARE @p1 Int = 1

SELECT [t0].[Title], [t1].[MenuID], [t1].[Title] AS [Title2], [t1].[Url], [t1].[MenuParent], [t1].[MenuType], (
    SELECT COUNT(*)
    FROM [Menu] AS [t2]
    WHERE ([t0].[MenuType] = @p0) AND (([t0].[MenuID]) = [t2].[MenuParent])
    ) AS [value]
FROM [Menu] AS [t0]
LEFT OUTER JOIN [Menu] AS [t1] ON ([t0].[MenuType] = @p0) AND (([t0].[MenuID]) = [t1].[MenuParent])
WHERE [t0].[MenuType] = @p1

Read More

Query samples on a self referenced table (Part-1)

I will give you some query examples in Linq, Lambda Expression and SQL syntax.
Examples are build on one table that includes self referenced data. We will create a menu table on the database and fill it with some sample data. Some menu items are top menus and the others are subs. Sub menu items has a parent id which is referenced another menu item on the same table.

Step 1: Create menu table on SQL Server.

CREATE TABLE [dbo].Menu(
 [MenuID] [int] IDENTITY(1,1) NOT NULL,
 [Title] [nvarchar](50) NULL,
 [Url] [nvarchar](100) NULL,
 [MenuParent] [int] NULL, --If has parent fill this column with MenuID 
 [MenuType] [int] NULL --1: Top menu, 2:Sub menu
)

Step 2: Insert some data

INSERT INTO [dbo].[Menu] ([Title], [Url], [MenuParent], [MenuType]) VALUES ('Accounts', '.aspx', 0, 1) --ID=1

INSERT INTO [dbo].[Menu] ([Title], [Url], [MenuParent], [MenuType]) VALUES ('Users', '.aspx', 1, 2) --ID=2

INSERT INTO [dbo].[Menu] ([Title], [Url], [MenuParent], [MenuType]) VALUES ('Customers', '.aspx', 1, 2) --ID=3

INSERT INTO [dbo].[Menu] ([Title], [Url], [MenuParent], [MenuType]) VALUES ('Settings', '.aspx', 0, 1) --ID=4

INSERT INTO [dbo].[Menu] ([Title], [Url], [MenuParent], [MenuType]) VALUES ('App', '.aspx', 4, 2) --ID=5

INSERT INTO [dbo].[Menu] ([Title], [Url], [MenuParent], [MenuType]) VALUES ('Web', '.aspx', 4, 2) --ID=6

INSERT INTO [dbo].[Menu] ([Title], [Url], [MenuParent], [MenuType]) VALUES ('Service', '.aspx', 4, 2) --ID=7

INSERT INTO [dbo].[Menu] ([Title], [Url], [MenuParent], [MenuType]) VALUES ('Parameters', '.aspx', 0, 1) --ID=8

INSERT INTO [dbo].[Menu] ([Title], [Url], [MenuParent], [MenuType]) VALUES ('Account Type', '.aspx', 8, 2) --ID=9

INSERT INTO [dbo].[Menu] ([Title], [Url], [MenuParent], [MenuType]) VALUES ('Help', '.aspx', 0, 1) --ID=10

Step 3: Query table. In this example we will see some basic queries.

Basic Queries

Queries below selects top menus and sub menus.

Linq

var topMenus = from f in Menus where f.MenuType==1 select f;
var subMenus = from f in Menus where f.MenuType==2 select f;

Lambda

Menus
   .Where (f => (f.MenuType == 1))

Menus
   .Where (f => (f.MenuType == 2))

SQL

DECLARE @p0 Int = 1
SELECT [t0].[MenuID], [t0].[Title], [t0].[Url], [t0].[MenuParent], [t0].[MenuType]
FROM [Menu] AS [t0]
WHERE [t0].[MenuType] = @p0
GO

DECLARE @p1 Int = 2
SELECT [t0].[MenuID], [t0].[Title], [t0].[Url], [t0].[MenuParent], [t0].[MenuType]
FROM [Menu] AS [t0]
WHERE [t0].[MenuType] = @p1
GO

See Part-2 for the other queries.

Read More