Unable to cast object of type 'system.int32' to type 'system.byte '.?

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The image is saved in access database in "Long binary data" format but when retrieving the same image cause an error in C#"
Unable to cast object of type 'system.int32' to type 'system.byte '.? "

Error:

Unable to cast object of type 'system.int32' to type 'system.byte '.? "

What I have tried:

View Image from access databse code:

private void ViewImage_Click(object sender, EventArgs e)
        {
            OleDbConnection connection = new OleDbConnection();
            connection.ConnectionString = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source =C:\Users\Shabbir\source\repos\Pricing\bin\Debug\Database\Pricing.accdb;
                Persist Security Info=False;";
            connection.Open();

OleDbCommand command = new OleDbCommand("select * From tbl_TestImage where Name='" + textBoxName.Text + "' ", connection);

         
            OleDbDataReader reader = command.ExecuteReader();

          while (reader.Read())
            {

                lbl_photoName.Text = reader[1].ToString();
                pictureBox1.Image = LoadPhoto((byte[])reader[3]);
            
               

            }
        }

        private Image LoadPhoto(byte[] photo)
        {
            MemoryStream ms = new MemoryStream(photo);
            return Image.FromStream(ms);
        }

    } }

Posted 6-Nov-19 22:54pm

Member 14647607

Updated 6-Nov-19 23:13pm

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OriginalGriff · Accepted Answer · 2019-11-06T23:14:00

That's full of bad ideas, I'm afraid.

First off: Never concatenate strings to build a SQL command. It leaves you wide open to accidental or deliberate SQL Injection attack which can destroy your entire database. Always use Parameterized queries instead.

When you concatenate strings, you cause problems because SQL receives commands like:

SQL

SELECT * FROM MyTable WHERE StreetAddress = 'Baker's Wood'

The quote the user added terminates the string as far as SQL is concerned and you get problems. But it could be worse. If I come along and type this instead: "x';DROP TABLE MyTable;--" Then SQL receives a very different command:

SQL

SELECT * FROM MyTable WHERE StreetAddress = 'x';DROP TABLE MyTable;--'

Which SQL sees as three separate commands:

SQL

SELECT * FROM MyTable WHERE StreetAddress = 'x';

A perfectly valid SELECT

SQL

DROP TABLE MyTable;

A perfectly valid "delete the table" command

SQL

--'

And everything else is a comment.
So it does: selects any matching rows, deletes the table from the DB, and ignores anything else.

So ALWAYS use parameterized queries! Or be prepared to restore your DB from backup frequently. You do take backups regularly, don't you?

Secondly, never hardcode connections strings - they should always be held in a config file of some form.

Thirdly, you shouldn't use SELECT * FROM, and you very particularly should never use SELECT * FROM and then access the resulting data via numeric indexes: if the database gets modified, your code breaks in nasty ways, which can end up corrupting your DB beyond repair.
And it's inefficient as well - never SELECT columns you don't intend to use!
Instead use SELECT Column1, Column2 FROM and list the actual columns you are interested in - then access those via a numeric (or better text) index. It makes for more reliable software, as well as more readable and maintainable.

And most likely, that will fix your problem - I suspect that the column with index 3 you are returning is not the image data at all but an integer value...

Unable to cast object of type 'system.int32' to type 'system.byte '.?

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Unable to cast object of type 'system.int32' to type 'system.byte '.?

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