How to show/handle Image from Database?

Create a generic handler like
// DBImageHandler.ashx

    <%@ WebHandler Language="C#" Class="DbImageHandler" %>

    using System;

    using System.Web;

    using System.IO;

    public class DbImageHandler : IHttpHandler

    {

    public void ProcessRequest(HttpContext context)

    {

    Int32 id;

    if (context.Request.Params["id"] != null)

        id = Convert.ToInt32(context.Request.Params["id"]);

    else

        throw new ArgumentException("No parameter specified");

    context.Response.ContentType = "image/jpeg";

    Stream strm = getDBImage(id);

    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);

    }

    }

    public Stream getDBImage(int id)

    {

    System.Data.SqlClient.SqlDataAdapter da = new System.Data.SqlClient.SqlDataAdapter("SELECT photo FROM  Employee WHERE EmployeeID=" + id, System.Configuration.ConfigurationManager.ConnectionStrings["DBConStr"].ConnectionString);

    System.Data.DataTable dt = new System.Data.DataTable();

    da.Fill(dt);

    if (dt.Rows.Count == 0)

        return null;

    return new MemoryStream((byte[])dt.Rows[0]["photo"]);

    }

    public bool IsReusable

    {

    get

    {

        return false;

    }

    }

    }

Now you can use Image link as
DbImageHandler.ashx?id=1

Exmaple :

<img src="DbImageHandler.ashx?id=1" alt="Employee 1 Photo" width="400px" height="400px" />

How to Cross-thread operation

The same control can't be accessed by multiple threads. in that case the following code is helpful

private void Form1_Load(object sender, EventArgs e)

{

    Thread t1 = new Thread(new ParameterizedThreadStart(printThr1));

    Thread t2 = new Thread(printThr2);

    t1.Start("U");

    t2.Start();

}

private void printThr1(object t)

{

           

    for(int i=1;i<600000;i+=2)

    {

        if (txtControl.InvokeRequired)

        {

            txtControl.Invoke(new MethodInvoker(delegate { txtControl.Text += Environment.NewLine + t.ToString()+"= " + i; }));

            Thread.Sleep(500);

        }

    }

}

private void printThr2()

{

           

    for (int i = 0; i < 50000; i += 2)

    {

              

        if (txtControl.InvokeRequired)

        {

            txtControl.Invoke(new MethodInvoker(delegate { txtControl.Text += Environment.NewLine + "N= " + i; }));

            Thread.Sleep(300);

        }

    }

}

How to load DLL and call its methods using C#.NET

// Unbox it to correct object

Type type = null;

String AssemblyDir = @"D:\Project\DataAccess.dll";

//AssemblyDir = AssemblyDir.TrimStart("file:\\".ToArray());

 Assembly a = Assembly.LoadFrom(AssemblyDir);

       type = a.GetType("DataAccess.DerivedClass");

   if (type != null)

       {

          BaseClass objBaseClass = (BaseClass)Activator.CreateInstance(type, args);

          resultCode = objBaseClass.MethodName(Parameters);

        }

       else

          {

              throw new Exception("Can't find correct type name or dll!"); // FATAL ERROR. Can't find correct type name or dll.

            }

Where  BaseClass is like

public class BaseClass : ICloneable

{

// this method is override by DerivedClass

 public virtual string MethodName( parameters )

 {

   throw new NotImplementedException();

 }

}

Where  DerivedClass is like

public class DerivedClass : BaseClass

{

public override sealed string MethodName(parameters)

{

// do something with parameters

}

}