C# Discussion Boards - CodeProject

Re: Multiple reads of a file when it is open in another application ?

1-Jan-15 6:12

I wonder if it's Notepad also monitoring the file it "has open" even though it's closed it so that it can track changes outside the editor - I use PSPad which does that - and the two processes are getting the notification at the same time and one is finding the file in use as a result?
Might be worth a sleep-retry-sleep-retry to give it another chance?

Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...

BillWoodruff1-Jan-15 21:55

BillWoodruff

1-Jan-15 21:55

Thanks again, Griff,

I am able to work around the problem by simply copying the dragged-dropped/changed file, then reading/processing the copied file, then deleting the copy. So, obviously, I do not alter the original in this scenario.

cheers, Bill

«A man will be imprisoned in a room with a door that's unlocked and opens inwards ... as long as it does not occur to him to pull rather than push» Wittgenstein

Re: Multiple reads of a file when it is open in another application ?

OriginalGriff1-Jan-15 23:05

Re: Multiple reads of a file when it is open in another application ?

1-Jan-15 23:05

If I helped, then you are welcome! Laugh | :laugh:

Somehow, I don't think I did...

Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...

Pete O'Hanlon1-Jan-15 23:04

Pete O'Hanlon

1-Jan-15 23:04

Bill, can I ask why you're reading the file contents in this way? You do a File.Open, create a StreamReader and associate it with the file, then you don't do anything with it? Instead, you do File.ReadAllLines on the file. Why not just use File.ReadAllLines instead? It opens, reads and closes the file.

Re: Multiple reads of a file when it is open in another application ?

BillWoodruff2-Jan-15 2:22

BillWoodruff

2-Jan-15 2:22

Thanks, Pete,

Yes, you're absolutely right; OriginalGriff pointed this out to me, and ... my bad ... I have not corrected the code.

cheers, Bill

«A man will be imprisoned in a room with a door that's unlocked and opens inwards ... as long as it does not occur to him to pull rather than push» Wittgenstein

Reference to array element

Krishnakumartg31-Dec-14 22:55

Krishnakumartg

31-Dec-14 22:55

In C++, we can add reference to an array element as shown below:

int aArray[50];
int& Ref = aArray[1];

How do we do the same in C#?

OriginalGriff31-Dec-14 23:56

31-Dec-14 23:56

You don't.
An int is not a reference type - it's a value type. You cannot "take a reference" to a value type.
The closest you can come is to pass the array element by reference to a method:

public void ChangeIt(ref int x) { x += 1; }

    ...
    int[] aArray = Enumerable.Range(1, 50).ToArray();

    ChangeIt(ref aArray[3]);

C++ and C# just share sufficient syntax to look similar: they are very different languages, and you should not try to "force" c++ ways of working on C# - it will end in tears...

Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...

BillWoodruff1-Jan-15 4:24

BillWoodruff

1-Jan-15 4:24

Just to add a minor-key note to this post:

If you are going to need to change a lot of values in an Array, you can pass the entire Array by reference.

«A man will be imprisoned in a room with a door that's unlocked and opens inwards ... as long as it does not occur to him to pull rather than push» Wittgenstein

OriginalGriff1-Jan-15 4:34

1-Jan-15 4:34

You don't need to - an array is a reference type anyway (even if it's an array of value type elements) so you can do this and it'll work:

    int[] arr = Enumerable.Range(1, 50).ToArray();
    ChangeIt(arr);
    ...

public void ChangeIt(int[] arr)
    {
    for (int i = 0; i < arr.Length; i++)
        {
        arr[i]++;
        }
    }

Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...

harold aptroot1-Jan-15 4:44

harold aptroot

1-Jan-15 4:44

There is no such thing as a "local variable which is a reference" in C#, but there is in the underlying MSIL and runtime. That doesn't do you much good, but it might be interesting to know.

[Solved]C# Database Image Manager

Krishnakumartg26-Jan-15 18:52

Krishnakumartg

26-Jan-15 18:52

Got it. Thanks...

rattlerrFx31-Dec-14 10:44

31-Dec-14 10:44

My Database Development book includes a program for inserting Images into a database after studying the code and modifying just the connection string and image's directory. When i run the program even with Administrator it produces a Run Time error of "Denied" in the message box. Now the program does connect to the database and does insert values into the Primary Key column and 2 other columns. The problem is that it is not reading the Folder that contains the images and is not inserting them into the database image column.

I have modified the folder's permissions for Full Control but during execution of the software it automatically produces the error message of Denied.The Database has been setup for FILESTREAM and Filestream access level has been modified for level 2 and setup in the Sql Server Properties under FileStream.

Any idea's on what may be causing this issue? I am running Windows 8.1 Pro 64Bit

Class

using System;
using System.Collections.Generic;
using System.Data.SqlClient;
using System.Data.SqlTypes;
using System.IO;

namespace MusicStoreImageManager
{
    class ProductDB
    {
        // define the directory for the images
        static string imagesPath = "C:/Users/Rattlerr/Pictures/Images/";

        public static SqlConnection GetConnection()
        {
            SqlConnection connection = new SqlConnection();
            connection.ConnectionString =
                "Data Source=RATTLERR;Initial Catalog=Test;Integrated Security=False;User ID=sa;Password=SomePassword";
            return connection;
        }

        public static void WriteImage(int productID, string imageName)
        {
            SqlConnection connection = null;
            SqlTransaction transaction = null;
            try
            {
                // 1. Set up the input stream from the image file
                string filepath = imagesPath + imageName;
                if (File.Exists(filepath) == false)
                    throw new Exception("File Not Found: " + filepath);

                FileStream sourceStream = new FileStream(
                    filepath,
                    FileMode.Open,
                    FileAccess.Read);

                // 2. Initialize the row in the table
                connection = GetConnection();

                SqlCommand command = new SqlCommand();
                command.Connection = connection;
                command.CommandText =
                    "INSERT INTO ProductImages " +
                    "VALUES (@ProductID, " +
                    "        CAST(@RowID AS uniqueidentifier), 0)";

                Guid rowID = Guid.NewGuid();
                command.Parameters.AddWithValue("@ProductID", productID);
                command.Parameters.AddWithValue("@RowID", rowID);

                connection.Open();
                command.ExecuteNonQuery();

                // 3. Get a reference to the BLOB
                transaction = connection.BeginTransaction();
                command.Transaction = transaction;
                command.CommandText =
                    "SELECT ProductImage.PathName(), " +
                    "       GET_FILESTREAM_TRANSACTION_CONTEXT() " +
                    "FROM ProductImages " +
                    "WHERE RowID = CAST(@RowID AS uniqueidentifier)";
                command.Parameters.Clear();
                command.Parameters.AddWithValue("@RowID", rowID);

                SqlDataReader reader = command.ExecuteReader();
                if (reader.Read() == false)
                    throw new Exception("Unable to get path and context for BLOB.");
                string path = (string)reader[0];
                byte[] context = (byte[])reader[1];
                reader.Close();

                // 4. Set up the output stream to the database
                SqlFileStream targetStream = new SqlFileStream(path, context, FileAccess.Write);                

                // 5. Read from file and write to database
                int blockSize = 1024 * 512;
                byte[] buffer = new byte[blockSize];
                int bytesRead = sourceStream.Read(buffer, 0, buffer.Length);
                while (bytesRead > 0)
                {
                    targetStream.Write(buffer, 0, bytesRead);
                    bytesRead = sourceStream.Read(buffer, 0, buffer.Length);
                }

                targetStream.Close();
                sourceStream.Close();
                transaction.Commit();
            }
            catch (Exception e)
            {
                if (transaction != null)
                    transaction.Rollback();
                throw e;
            }
            finally
            {
                if (connection != null)
                    connection.Close();
            }
        }

        public static Byte[] ReadImage(int imageID) 
        {
            SqlConnection connection = null;
            SqlTransaction transaction = null;
            try 
            {
                connection = GetConnection();
                connection.Open();
                transaction = connection.BeginTransaction();

                SqlCommand command = new SqlCommand();
                command.Connection = connection;
                command.Transaction = transaction;
                command.CommandText =
                    "SELECT ProductImage.PathName(), " +
                    "       GET_FILESTREAM_TRANSACTION_CONTEXT() " +
                    "FROM ProductImages " +
                    "WHERE ImageID = @ImageID";

                command.Parameters.AddWithValue("@ImageID", imageID);

                SqlDataReader reader = command.ExecuteReader();
                if (reader.Read() == false)
                    throw new Exception("Unable to get path and context for BLOB.");
                string path = (string)reader[0];
                byte[] context = (byte[])reader[1];
                reader.Close();

                // Set up the input stream from the database
                SqlFileStream sourceStream = new SqlFileStream(path, context, FileAccess.Read);                

                int blockSize = 1024 * 512;
                byte[] buffer = new byte[blockSize];
                List<byte> imageBytes = new List<byte>();
                int bytesRead = sourceStream.Read(buffer, 0, buffer.Length);
                while (bytesRead > 0)
                {
                    bytesRead = sourceStream.Read(buffer, 0, buffer.Length);
                    foreach(byte b in buffer)
                        imageBytes.Add(b);                        
                }
                sourceStream.Close();

                return imageBytes.ToArray();
            }
            catch (Exception e) 
            {
                throw e;
            }
            finally 
            {
                if (connection != null)
                    connection.Close();
            }
        }

        public static List<int> GetImageIDList()
        {
            SqlConnection connection = null;
            try
            {
                connection = GetConnection();

                SqlCommand command = new SqlCommand();
                command.Connection = connection;
                command.CommandText = 
                    "SELECT ImageID FROM ProductImages " +
                    "ORDER BY ImageID";

                connection.Open();
                SqlDataReader reader = command.ExecuteReader();
 
                List<int> imageIDList = new List<int>();
                while (reader.Read())
                {
                    int imageID = (int)reader[0];
                    imageIDList.Add(imageID);
                }
                reader.Close();

                return imageIDList;
            }
            catch (Exception e)
            {
                throw e;
            }
            finally
            {
                if (connection != null)
                    connection.Close();
            }
        }
    }
}

Main Form Code

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

using System.IO;

namespace MusicStoreImageManager
{
    public partial class ImageManagerForm : Form
    {
        public ImageManagerForm()
        {
            InitializeComponent();
        }

        private void LoadImageIDComboBox()
        {
            // load the combo box
            List<int> imageIDList = ProductDB.GetImageIDList();
            foreach (int i in imageIDList)
                imageIDComboBox.Items.Add(i);
        }

        private void ImageManagerForm_Load(object sender, EventArgs e)
        {
            this.LoadImageIDComboBox();
            imageIDComboBox_SelectedIndexChanged(sender, e);
        }

        private void imageIDComboBox_SelectedIndexChanged(
            object sender, EventArgs e)
        {
            try
            {
                int imageID = Convert.ToInt32(imageIDComboBox.Text);

                // read image bytes from the database and display in picture box
                Byte[] imageByteArray = ProductDB.ReadImage(imageID);
                MemoryStream ms = new MemoryStream(imageByteArray);
                imagePictureBox.Image = System.Drawing.Image.FromStream(ms);
                ms.Close();
            }
            catch (Exception ex)
            {
                MessageBox.Show(this, ex.Message, "Error");
            }
        }

        private void uploadButton_Click(object sender, EventArgs e)
        {
            try
            {
                int productID = Convert.ToInt32(productIDTextBox.Text);
                string filename = filenameTextBox.Text;
                ProductDB.WriteImage(productID, filename);
                MessageBox.Show(this, "Image upload was successful!", 
                    "Upload Confirmation");

                // refresh combo box
                imageIDComboBox.Items.Clear();
                this.LoadImageIDComboBox();
            }
            catch (Exception ex)
            {
                MessageBox.Show(this, ex.Message, "Error");
            }
        }
    }
}

modified 3-Jan-15 12:31pm.

Richard Andrew x6431-Dec-14 11:13

31-Dec-14 11:13

It would help a great deal if you pointed out which line of code is generating the Access Denied message.

The difficult we do right away...
...the impossible takes slightly longer.

rattlerrFx31-Dec-14 11:25

31-Dec-14 11:25

That's the whole problem the code doesn't produce an error or warnings during Debug or compilation just at Run time the error message pops up in a Message Box. The program is suppose to read the folder and load the image into the Image Picture Box nor will it upload the image to the database. The image column just shows 0x0000000 that is because none of the images are being loaded into the Image column for the table.

It will put information into the other columns just not the image, I cannot figure out if it is a permissions issue. Now when i select a different ImageID from the dropdown box the error will repeat itself here is the code below.

private void imageIDComboBox_SelectedIndexChanged(
           object sender, EventArgs e)
       {
           try
           {
               int imageID = Convert.ToInt32(imageIDComboBox.Text);

               // read image bytes from the database and display in picture box
               Byte[] imageByteArray = ProductDB.ReadImage(imageID);
               MemoryStream ms = new MemoryStream(imageByteArray);
               imagePictureBox.Image = System.Drawing.Image.FromStream(ms);
               ms.Close();
           }
           catch (Exception ex)
           {
               MessageBox.Show(this, ex.Message, "Error");
           }
       }

modified 31-Dec-14 17:34pm.

Richard Andrew x6431-Dec-14 11:27

31-Dec-14 11:27

What you say makes no sense. "Debug" is runtime, is it not? You're running the program in the debugger, right?

The difficult we do right away...
...the impossible takes slightly longer.

rattlerrFx31-Dec-14 11:36

31-Dec-14 11:36

Doesn't matter if i run it in the debugger or the compiled executable the same error repeats itself. I have modified the folder permissions to full control and even tried running the program under administrative privileges.

Richard Andrew x6431-Dec-14 11:39

31-Dec-14 11:39

OK I think I understand what you mean. You mean the program is not breaking with an unhandled exception.

One big problem with your code is that you have so many different operations all encompassed within single try/catch blocks that it's hard to tell where the exception is coming from.

If you were to temporarily comment out the try/catch blocks, but leave the code they contain, then the exception will become plain.

The difficult we do right away...
...the impossible takes slightly longer.

rattlerrFx31-Dec-14 11:45

31-Dec-14 11:45

I will try that this code is not mine it was written by the author of the book murachs Sql Server 2012 for Developers. When i run the Debugger a message box pops up and says Error "Access is Denied". If i press the Okay button the program continues and loads the main form but the picture box is empty because the image columns are empty.

Now if i enter a productID into the textbox and press the upload button it will insert the productID into the productID column and generate a ImageID and RowID. The program is setup to look in the images folder, you type the image name for example "picture.jpg" into the textbox put in the productID number into the textbox and press the upload button.

static string imagesPath = "C:/Users/Gerry/Pictures/Images/";

modified 31-Dec-14 17:57pm.

Richard Andrew x6431-Dec-14 12:00

31-Dec-14 12:00

Well, finding out exactly which line of code is causing the exception is the first step to solving the problem.

Could it be that the path you point out does not exist on your machine?

The difficult we do right away...
...the impossible takes slightly longer.

rattlerrFx31-Dec-14 12:08

31-Dec-14 12:08

The path does exist for the fact that i created the folder and set the permissions to full control. Now i am starting to think it might be a database permissions issue even thou it does connect to the database under the SA user role for authentication. The connection string works just fine i have another program that will log in and retrieve data from the database and load it into a DataGrid. Below is the TSQL i used to create the Database and FILESTREAM and I made sure the FILESTREAM is turned on under the SQL Server Configuration Manager.

SQL

CREATE DATABASE medical
ON PRIMARY
(
   NAME = medical,
   FILENAME = 'C:\Program Files\Microsoft SQL Server\MSSQL12.MSSQLSERVER\MSSQL\DATA\medical.mdf'),
   FILEGROUP FileSteamImages CONTAINS FILESTREAM DEFAULT 
   (
   NAME = medicalImages,
   FILENAME = 'C:\Program Files\Microsoft SQL Server\MSSQL12.MSSQLSERVER\MSSQL\DATA\medical_images');
   GO

Here is the code i used to elevate the permissions:

SQL

EXEC sp_configure filestream_access_level, 2;
RECONFIGURE;

Richard Andrew x6431-Dec-14 12:11

31-Dec-14 12:11

rattlerrFx wrote:
Now i am starting to think it might be a database permissions issue

There's no use making a guess. Try doing what I said, and you'll find out exactly what's wrong.

The difficult we do right away...
...the impossible takes slightly longer.

rattlerrFx31-Dec-14 12:20

31-Dec-14 12:20

No luck i commented out every try and catch block in the entire program still generates the same error. I think the error is being generated by the SQL Server.

Richard Andrew x6431-Dec-14 12:24

31-Dec-14 12:24

I find that hard to believe since the function that's generating the messagebox is itself inside a catch block. Are you sure you commented out every try/catch block?

The difficult we do right away...
...the impossible takes slightly longer.

rattlerrFx31-Dec-14 12:24