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I have been looking at a few projects about cryptography.
Now the thing i can't figure out is why do string become longer in size when encrypted and files don't?
strings easily double in size "test" because 24 chars long.
But when i encrypted a 5.04MB picture the size remained exactly the same to the byte, and it was encrypted fully.
I used this project:
http://www.codeproject.com/KB/recipes/Encrypt_Decrypt_File_Data.aspx[^]
Although i think the same goes for all projects.
Thanks for reading.
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Many algorithms encrypt block by block. The minimum you can encrypt is one block, which is why your short string ends up bigger when encrypted (it gets padded out to a full block).
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Encryption deals with bytes, so if you encrypt from a string to a string you first encode the string into bytes, encrypt, then represent the encrypted bytes as a string.
If you use UTF-16 (Encoding.Unicode.GetBytes method) to encode the string, each character is stored as two bytes. If you then represent the encrypted bytes as a string in hexadecimal format, it doubles again. Using base-64 to represent the bytes as a string is more compact, as it only adds another 33%.
The UTF-8 encoding is more compact, as it stores the most common characters in a single byte.
Despite everything, the person most likely to be fooling you next is yourself.
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I am using Visual Studio 2008 for the first time. I am trying to consume a web service by using a local copy of the WSDL. The actual web service is up and running, but it does not have a public WSDL or Discovery files. I have the acutal WSDL and a couple of XSD documents on my local machine, but I can't figure out how to get VS to use it.
When I click "Add Web Reference", it expects a URL. When I navigate to my local file system, it shows "Access to the path is denied". I have the group "Everyone" set to full control on this directory thinking it was a permission problem.
What am I doing wrong? I just upgraded from 2003 to 2008 and am having culture shock!
Thanks in advance...
-Scott
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I'm filling a datagridview with rows of data and upon selection (RowEnter event) of a full row the primary key is copied into a textbox which is then used as a foreign key in another table and gives me the quantity of rows containing the foreign key.
This is fine and dandy, except when I click on the DataGridView headers it throws an exception:
Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index
Any ideas as to why this is occurring? Thanks in advance!
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Well, I got around the issue with a try/catch block. Out of curiosity, however, I'd love to know if there are other alternatives to this. 
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Hi all,
I have two aspx pages which have one gridview table each. the second gridview is dependent on the other based on which row you select in the first gridview table.
Ive used the configuraztion wizard for the 2nd table to generate the table based on the session value ie Session["Selection"].
However the problem occurs when, Im using session values between the pages, and when the event handler is fired, it doesnt transfer the session value to the next page and hence the 2nd pages shows nothing.
I managed succeed in doing this in another project and have compared it many a time yet I cannot spot the difference in the way I have coded this. Yet one works and the other doesnt.
Heres my code. Thanks + Cheers
1st page
protected void ViewCustomer(object sender, EventArgs e)
{
Session["Selection"] = GridView1.SelectedDataKey.Value
Response.Redirect("~/Master/SelectionBetweenTwoPagesPageTwo.aspx");
}
<asp:gridview id="GridView1" runat="server" autogeneratecolumns="False" xmlns:asp="#unknown">
CellPadding="4" DataKeyNames="CustomerID" DataSourceID="SqlDataSource1"
ForeColor="#333333" GridLines="None" Height="139px"
OnSelectedIndexChanged="ViewCustomer" Width="448px">
<footerstyle backcolor="#990000" font-bold="True" forecolor="White" />
<rowstyle backcolor="#FFFBD6" forecolor="#333333" />
<columns>
<asp:boundfield datafield="CustomerID" headertext="CustomerID" readonly="false">
SortExpression="CustomerID" />
<asp:boundfield datafield="CompanyName" headertext="CompanyName">
SortExpression="CompanyName" />
<asp:boundfield datafield="ContactName" headertext="ContactName">
SortExpression="ContactName" />
<asp:boundfield datafield="ContactTitle" headertext="ContactTitle">
SortExpression="ContactTitle" />
<asp:hyperlinkfield navigateurl="~/Master/SelectionBetweenTwoPagesPageTwo.aspx">
Text="View" />
</asp:hyperlinkfield></asp:boundfield></asp:boundfield></asp:boundfield></asp:boundfield></columns>
<pagerstyle backcolor="#FFCC66" forecolor="#333333" horizontalalign="Center" />
<selectedrowstyle backcolor="#FFCC66" font-bold="True" forecolor="Navy" />
<headerstyle backcolor="#990000" font-bold="True" forecolor="White" />
<alternatingrowstyle backcolor="White" />
</asp:gridview>
<asp:sqldatasource id="SqlDataSource1" runat="server" xmlns:asp="#unknown">
ConnectionString="<%$ ConnectionStrings:NORTHWNDConnectionString %>"
SelectCommand="SELECT [CustomerID], [CompanyName], [ContactName], [ContactTitle] FROM [Customers]">
</asp:sqldatasource>
protected void Page_Load(object sender, EventArgs e)
{
if (Session["Selection"] != null)
{
int customerid = (int)Session["Selection"];
}
}
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CrimeanTurtle2008 wrote: //2nd page
protected void Page_Load(object sender, EventArgs e)
{
if (Session["Selection"] != null)
{
int customerid = (int)Session["Selection"];
}
}
This above code does nothing useful. You test if there is something in the session. If so you capture it in to a local variable (that does not exist outside the scope of the Page_Load method) and does nothing with it.
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I have debugged this process step by step and, indeed it doesnt do much. However I have solved this problem now as I realised that the datatype should have been a string instead of an integer. Thanks again Colin.
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I cannot figure this out..
Basically I read the bytes from my database, saved it to he harddrive, then attached it to an email, then delete the file. So I wanted to put this in a stream or memorystream then attach it to an email so I skip all the file saving.
myReader = cmd.ExecuteReader();
while (myReader.Read())
{
FileData = myReader["Saved_File"].ToString();
byte[] buffer = new byte[FileData.Length];
ms.Read(buffer, 0, FileData.Length);
mm.Attachments.Add(new Attachment(ms, myReader["Filename"].ToString()));
}
It attaches, but only up to 77 bytes. I'm lost.. In my database it is stored as a varbinary(MAX).
It works if I save it to the harddrive. I just want to skip all of that.
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Jacob D Dixon wrote: FileData = myReader["Saved_File"].ToString();
Is Saved_File the byte array or is for example the original name of the file? I would guess, that you have used it for both purposes because later you have:
Jacob D Dixon wrote: byte[] buffer = new byte[FileData.Length];
Also your post doesn't show how the memory stream is constructed or what's the type of FileData so it's quite hard to say if they are correctly.
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I'm sorry I have never done this before.
What I have there is what I've tried to get to work from what I've seen on the internet.
myReader["Saved_File"].ToString(); is reading the varbinary from the SQL database (Saved_File) column.
So i'm taking the string FileData and storing the information in the SQL database in the string.
So what I'm trying to do is take the data from the database and attach it in an email without actually saving a file to the harddrive then deleting it when I'm done. I'm wanting to store the file in memory, then attach it to the email and send it. Is this possible?
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You have to loop on the read in order to get all of the data from the stream. The read method returns number of bytes read, loop until number of bytes read == number of bytes in file.
Also, to string will only cause things to break. It is the most overused and misunderstood feature of .NET apparently.
Need software developed? Offering C# development all over the United States, ERL GLOBAL, Inc is the only call you will have to make.
If you don't ask questions the answers won't stand in your way.
Most of this sig is for Google, not ego.
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Jacob D Dixon wrote: FileData = myReader["Saved_File"].ToString();
You are getting the data as a byte array, but then you call the ToString method on the data. The Array class does not override the ToString method, so you are using the default implementation, which returns the name of the class. So, that line gives the same result as:
FileData = "System.Byte[]";
Jacob D Dixon wrote: byte[] buffer = new byte[FileData.Length];
Here you are creating a new byte array with the size 13.
Jacob D Dixon wrote: ms.Read(buffer, 0, FileData.Length);
Here you attemt to read the first 13 bytes from the memorystream. However, as you ignore the return value of the Read method, you don't know if you got one byte or 13 bytes. The Read method doesn't have to return the number of bytes that you requested, even if there are more bytes left in the stream, so you need to call Read in a loop until you have got all the data that you want, or until the method returns zero which means that it reached the end of the stream.
However, I have no idea why you are trying to read the data from the memory stream into a byte array, when you are using the memory stream in the attachment. Also I don't know where you think that you get the data from the data reader into either the memory stream or the buffer...
Despite everything, the person most likely to be fooling you next is yourself.
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Im not trying to read from a memorystream into a byte array. I'm trying to take the bytes from the database and put them into a Stream to attach to an email.
Attachment of (System.Net.Mail) needs a file or a Stream
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Figured it out. This is what I did:
...(SqlConnection, SqlCommand stuff up here)...
MailMessage mm = new MailMessage(...);
SqlDataReader myReader = null;
conn.Open
myReader = cmd.ExecuteReader();
while (myReader.Read())
{
object buffer = myReader["Saved_File"];
mm.Attachments.Add(new Attachment(new MemoryStream((byte[])buffer), myReader["Filename"].ToString()));
}
conn.Close();
It works.. but is that a good way to do it. Basically tehre can be multiple files per ticket. So it goes through each file within the ticket (that has the ID of whatever) and puts it in the object buffer, then attaches it to an email.
Is there a better way? I tested this and it works but I would love to learn a better or more correct way.
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I think that overall the solution is good. It's definitely better to process the data in memory rather than writing it to disk only to delete it right afterwards. Especially since the only reason for writing to disk was to use the file as an Attachment. Writing to disk is slower and more 'risky' than working with the data in memory. One small improvement would be to put a try/catch/finally around the while loop and use the finally clause to close the database resources. Another would be to declare buffer as the correct type just one time outside the loop and use safe type conversion followed by testing it for null. Another thing to improve might be accessing the 'Filename' field without testing for DBNull or anything; but that may not be an issue for your data (you might have the field declared not null in the database, or might be defaulting it to '' if it's null in your query, etc.).
try
{
byte[] buffer = null; <----- declare it here as null and of type byte[]
while(myReader.Read())
{
buffer = myReader["Saved_File"] as byte[]; <----- safely convert the return value here
if(buffer == null) <----- conversion failed, skip this item
continue;
mm.Attachments.Add(new Attachment(new MemoryStream(buffer), myReader["Filename"].ToString()));
}
}
catch
{
}
finally <----- close out database resources here
{
if(myReader != null)
myReader.Close();
if(conn != null)
conn.Close();
}</handle>
Keep It Simple Stupid! (KISS)
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If I have a .dll project with a bunch of common classes, can I add that project to multiple solutions? Is this a safe thing to do or is there a better solution?
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mobius111001 wrote: .dll project
Why not just reference the DLL in whatever project you want to use it in instead of adding the project all the time?
Why is common sense not common?
Never argue with an idiot. They will drag you down to their level where they are an expert.
Sometimes it takes a lot of work to be lazy
Individuality is fine, as long as we do it together - F. Burns
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If I wanted to add new features to the DLL or something of that nature.
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mobius111001 wrote: add new features to the DLL
That does not preclude you adding new features.
Why is common sense not common?
Never argue with an idiot. They will drag you down to their level where they are an expert.
Sometimes it takes a lot of work to be lazy
Individuality is fine, as long as we do it together - F. Burns
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Yet, .Net is crap where code re-use is concerned. In C++, all you had to do was add a given file to your project, regardless of what folder it was in. In .net, you can't do that. I don't care to have a million little DLL's distributed with my app. Sometimes, I don't want ANY DlL's. Code re-use is limited to making a COPY of a file in the new project's folder. It's just crap, and a huge step AWAY from code re-use.
"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
-----
"...the staggering layers of obscenity in your statement make it a work of art on so many levels." - Jason Jystad, 10/26/2001
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Isn't using a Source Control product the modern version of pointing your C/C++ project to a file on your hard drive? 
led mike
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Nope, not when you're dealing with .Net.
"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
-----
"...the staggering layers of obscenity in your statement make it a work of art on so many levels." - Jason Jystad, 10/26/2001
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You can add source code as a link, I do that a lot when I don't want to include my whole library.
I agree (and have since my first experience with VS ten years ago) that VS should not copy files by default.
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