Displaying Image from Binary Data/Blob in asp.net

You should define your mime type at your image handler like that :

imageResponse.ContentType = "Image/Jpeg";

EDIT : It seems like you should change your image column like that. That one gets your volunteer name and pass it to your query string parameter :

<asp:Image ID="Image1" runat="server" ImageUrl='<%# 
       DataBinder.Eval(Container.DataItem, 
                       "VolunteerName", 
                       "~/ShowImage.ashx?VolunteerName={0}") 
       %>'/>

This is the DataAccessLayer

 public List<Volunteer> VolunteerTRetrieve()
    {
        List<Volunteer> vList = new List<Volunteer>();
        byte[] volunteerProfilePicture;
        MemoryStream ms = new MemoryStream();
        string volunteerName, volunteerNRIC, volunteerAddress, volunteerEmail, volunteerContact;
        string queryStr = "SELECT * FROM TVolunteer Order By VolunteerName";
        SqlConnection conn = new SqlConnection(DBconnStr);
        SqlCommand cmd = new SqlCommand(queryStr, conn);
        conn.Open();
        SqlDataReader dr = cmd.ExecuteReader();
        while ((dr.Read()))
        {
            volunteerName = dr["VolunteerName"].ToString();
            volunteerNRIC = dr["VolunteerNRIC"].ToString();
            volunteerAddress = dr["VolunteerAddress"].ToString();
            volunteerEmail = dr["VolunteerEmail"].ToString();
            volunteerContact = dr["VolunteerContact"].ToString();
            volunteerProfilePicture = (byte[])dr["VolunteerProfilePicture"];
            ms.Write(volunteerProfilePicture, 0, volunteerProfilePicture.Length);



            vList.Add(new Volunteer(volunteerName, volunteerNRIC, volunteerAddress, volunteerEmail, volunteerContact, volunteerProfilePicture));
        }
        conn.Close();
        dr.Dispose();
        return vList;
    }

This is BusinessLogicLayer

        public List<Volunteer> RetrieveAllTVolunteer()
    {
        Volunteer v = new Volunteer();
        List<Volunteer> vList = new List<Volunteer>();
        vList = v.VolunteerTRetrieve();
        return vList;
    }

This is Presentation Layer

List<Volunteer> allVolunteer = new List<Volunteer>();
            allVolunteer = vBLL.RetrieveAllTVolunteer();
            dl_tvolunteer.DataSource = allVolunteer;
            dl_tvolunteer.DataBind();

and the .aspx of Presentation Layer

    <asp:DataList ID="dl_tvolunteer" runat="server" CellPadding="3" 
        ForeColor="#333333" RepeatColumns="3"
    RepeatDirection="Horizontal" Width="375px" Height="193px" GridLines="Both">
        <ItemTemplate>
            <asp:Image ID="Image1" runat="server" ImageUrl='<%# DataBinder.Eval(Container.DataItem, "VolunteerProfilePicture","~/ShowImage.ashx?VolunteerName={0}") %>'  />
            <br />
            <asp:Label ID="lbl_Name" runat="server" Text='<%# Bind("VolunteerName") %>'></asp:Label>
            <br />
            <asp:Label ID="lbl_Contact" runat="server" Text='<%# Bind("VolunteerContact") %>'></asp:Label>
            <br />
            <asp:Label ID="lbl_Address" runat="server" Text='<%# Bind("VolunteerAddress") %>'></asp:Label>
            <br />
            <asp:Label ID="lbl_Email" runat="server" Text='<%# Bind("VolunteerEmail") %>'></asp:Label>
        </ItemTemplate>
    </asp:DataList>

and finally, my image handler class

public class ShowImage : IHttpHandler

{

public void ProcessRequest(HttpContext context)
{
    HttpRequest imageRequest = context.Request;
    HttpResponse imageResponse = context.Response;

    using (SqlConnection conn = new SqlConnection())
    {

        conn.ConnectionString = "Data Source=.\\SQLEXPRESS;AttachDbFilename=\"C:\\Users\\user\\Desktop\\ProjectA V2.9\\ProjectA \\ProjectA \\App_Data\\ProjectA .mdf\";Integrated Security=True;Connect Timeout=30;User Instance=True";
        string queryStr = "SELECT * FROM TVolunteer WHERE VolunteerName = @Name";
        string bQueryStr = "SELECT * FROM BVolunteer WHERE VolunteerName = @Name";

        imageResponse.ContentType = "image/jpeg";
        imageResponse.ContentType = "Image/png";
        SqlCommand bCMD = new SqlCommand(bQueryStr, conn);
        SqlCommand cmd = new SqlCommand(queryStr, conn);
        cmd.Parameters.AddWithValue("@Name", volunteerName);
        bCMD.Parameters.AddWithValue("@Name", volunteerName);
        conn.Open();

        SqlDataReader dr = cmd.ExecuteReader();


        while (dr.Read())
        {

            byte[] volunteerProfilePicture = (byte[])dr["VolunteerProfilePicture"];
            string volunteerName = dr["VolunteerName"].ToString();
            imageResponse.BinaryWrite(volunteerProfilePicture);


        }
        dr.Close();

        SqlDataReader bDR = bCMD.ExecuteReader();
        while (bDR.Read())
        {
            bDR.Read();

            byte[] volunteerProfilePicture = (byte[])bDR["VolunteerProfilePicture"];
            string volunteerName = bDR["VolunteerName"].ToString();
            imageResponse.BinaryWrite(volunteerProfilePicture);


            bDR.Close();
        }
    }
}

the error im getting from image handler is "Must declare the scalar variable "@Name"."