Develop Reference

Capture signature using HTML5 and save it as image to database

I am just starting to learn Jquery and working on asp.net webform app that will be used on a touchscreen device, and I need to capture user signature, basically user will sign and after hit save, I want their signature to be saved as an image to SQL server database so I can retrieve and display it later on a webpage.
I found this question: Capture Signature using HTML5 and iPad
and the jQuery plugin works great, exactly as I want.
Here the demo: http://szimek.github.io/signature_pad
Here the plug-in: https://github.com/szimek/signature_pad
So on the demo I see after hit "save" you will go to a new tab that display an image of your signed signature, and I noticed that the url is something like
data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAApIAAAE+CAYAAAA+vvBuAAAgAElEQVR4Xu3df8i37V0X8I/l0GY5BzZdiWslKhnNUaBR62lBP0htjuiHfz0uROgPmQsH/hE8jiKKjLl/IoLa9k+NMOYyhCRamyM0WI9bUBst5kzbUNfjxBlmaLy389jO+3q......
What does this url mean?
what type of variable will be used to store this in database table (nvarchar, binary...)
3 (MAIN QUESTION). How do I get those data text in code behind C# button click event to store them to a string variable for other purposes. Can someone provide a simple example so i can go from there?
if I am missing something please let me know, as I am looking at the .html file and those .js files in the demo project of that plugin, I am lost.

That URL is in BASE64 format. You can use that long string of characters in the SRC attribute of an image tag and it will be displayed.
To get better performance, the recommended way of storing photos is to store the image on the disk (using some kind of server side language) and then save the name of the file in a database as a CHAR or TEXT.
Not quite sure. I've never used the library before.

That is a Base64 encoded image.
data: says that data is following instead of a URL
image/png; specifies the content "mimetype" the data should be served as
base64, indicates the encoding type of the data
As base64 only uses ASCII characters, a varchar(MAX) would be suitable for storage. No need for nvarchar. I normally store the base64 encoding only (the last part after the comma), and keep the mime-type (e.g. image/png) in a separate field.
There are many options in C#. If you store the base64 part separately, you simplify the code a bit.
Turn it into an image server-side using byte[] imageBytes = System.Convert.FromBase64String(base64data) and creating an image from the byte array and type.
Inject the image into a webpage <img src="#Html.Raw("data:"+ mimetype + "base64," + base64data)"/>
Notes:
As #anthony mentions, your would typically store images as files (or in Blob storage nowadays) and only record the filename/URI. This depends on quantity size & usage.
We have found it convenient, for certain projects requiring extra security, for base64 images to be stored as encoded & encrypted strings in a database.
From comments: To save to, place the string value into a hidden input and update its value. It will then get posted back like any other string. Our own signature plugin just hides the original <input type="text"> it is attached to and puts the value there.

In addition to TrueBlueAussie's answer:
The simplest way to get your string in CodeBehind is:
Declare a HiddenField using ASP and assign a Static ID to it. (Static ID is important since ASP normally assigns automatically generated IDs to each control, and this can get difficult to predict).
Shape your JavaScript function in a way that SignaturePad writes the output base64 image string into this HiddenField. You can for example, use a button "Verify" that calls the Export function of the SignaturePad.
After the string is written into the HiddenField, read it back on CodeBehind. For this, you can use an additional button, for example something like "Save".
There are of course other options which are much more secure/versatile/appropriate, but this might be a good starting point for you.

Ms Word Doc Into Memory Stream and Saving As Char To Database

I want to read a ms word document exists in Desktop and save whole text to SQL database as Text, not Byte[]. Because the program written by the programmer works in company before me; coded the program will work like "only read NVARCHAR value from the column and show to user".
I tried using RichTextBox for saving text to the database converted from Abby Fine Reader but RTB Int32 Max Value supplies 2,147,483,647 chars. When I C/P the text(such as word doc including 100 pages, it only get 10-11-12 pages of char.)
And also viewed Memory Stream but as i said at the top of the topic: i dont want to save word chars as Byte[].
What is the way? I dont have any idea.

Inserting a byte array larger than 8k bytes

I'm using the code
cmd.Parameters.Add("#Array", SqlDbType.VarBinary).Value = Array;
The SqlDbType.VarBinary description states that it can only handle array's upto 8 K bytes. I have a byte array that represents an image and can go upto 10k bytes.
How do I store that in a varbinary(max) column using C#?
I have no trouble creating the array. I'm stuck at this 8k limit when trying to execute the query.
Edit: Let me clarify, on my machine even pictures upto 15k bytes get stored on the database in the varbinary(MAX) column when I run the asp.net application locally but once I deployed it the pictures would not get stored. I then resorted to drastically resizing the images to ensure their size was less that 8K and now the images get stored without any problem.

Perhaps you could look at the Sql Server FILESTREAM feature since its meant for storing files. It basically stores a pointer to your file and the file is stored directly in the filesystem (in the databases data directory).
I like FILESTREAM since you it means you continue to use the interface to the database (SQLClient for example) rather then breaking out to an adhoc method to read/write files to the harddrive. This means security is managed for you in that your app doesn't need special permissions to access the filesystem.
Quick google gave this acticle on using filestream in c# but I'm sure there are many others.
UPDATE following OP EDIT
So once deployed to other server the upload fails? Perhaps the problem is not the sql insert but that there is a http request content length limit imposed - for example in your web.config the httpRuntime element has the maxRequestLength attribute. If this is set to a low value perhaps this is the problem. So you could set to something like this (sets max to 6MB well over the 10kb problem):
<system.web>
<httpRuntime maxRequestLength="6144" />
The only thing here is the limit it 4MB buy default :|

No, this is what the description actually says:
Array of type Byte. A variable-length stream of binary data ranging
between 1 and 8,000 bytes. Implicit conversion fails if the byte array
is greater than 8,000 bytes. Explicitly set the object when working
with byte arrays larger than 8,000 bytes.
I would assume that what that actually means is that you cannot use AddWithValue to have a parameter infer the type as VarBinary if the byte array is over 8000 elements. You would have to use Add, specify the type of the parameter yourself and then set the Value property, i.e. use this:
command.Parameters.Add("#MyColumn", SqlDbType.VarBinary).Value = myByteArray;
rather than this:
command.Parameters.AddWithValue("#MyColumn", myByteArray);

Adding the length of data seems to be the fix
var dataParam = cmd.Parameters.AddWithValue("#Data", (object)data.Data ?? DBNull.Value);
if (data.Data != null)
{
dataParam.SqlDbType = SqlDbType.VarBinary;
dataParam.Size = data.Data.Length;
}

Invalid length for a Base-64 char array Exception under Chrome

I have to send images generated by a javascript function to the server.
In order to do it, I store the base64 string of the image in a hidden textbox.
myTextBox.value = 'imagedata';
It works well for small size files (1MB or less).
However, when I try to send large files, the server returns an "Invalid length for a Base-64 char array" error.
The weird part is that I get this error with Chrome but not with Internet Explorer 10.
When I check the value of the string with the debugger, it seems like it is truncated with Chrome.
What causes this problem ? Is there a workaround ?
Thank you.

You shouldn't be using a single textbox to hold that much content.
Textboxes can only hold a limited amount of content. Looks like you're hitting that limit in chrome.
If you really must store that much content, then you'll have to break the content across multiple textboxes.
The max size depends from browser to browser.
See here for more information

It could be because QueryString is returning space instead of + (it does that in Chrome, but not I.E.).
Solution:
Decrypt(Request.QueryString["myvar"].Replace(' ', '+'))

SQL Server CE 3.5 cuts off strings early (C#)

Hey Everyone, I am writing some code that makes use of SQL Server CE 3.5 and I am having a very strange problem. I have a string field in one of the tables that needs to store a full file path.
Over the course of trying to fix this problem I have that field set as nvarchar with a max size of 4000, but it is still cutting longer strings that are much shorter than the limit off
for example:
D:\iTunes\iTunes Media\Music\Abigail Williams\In The Absence Of Light\02 Final Destiny Of The Gods.m
This is clearly smaller than 4000 characters, yet it is missing the p3 at the end of the string.
I am using a table adapter to enter the data into the database with the following query:
INSERT INTO [Track] ([Artist_ID], [Album_ID], [FilePath], [LastUpdate])
VALUES (#Art, #Al, #Fp, #LU)
I know that the strings are fully formed on insert because I am using the following code to check:
if(!temp.Filepath.EndsWith(".mp3"))
MessageBox.Show("File Error");
this.trackTableAdapter1.InsertQuery(ArtID, AlID, temp.Filepath, File.GetLastWriteTime(temp.Filepath));
The message box does not get shown, so the string must end correctly on insert.
the query that extracts the data is:
SELECT
*
FROM Track
WHERE Artist_ID=#Artist_ID AND Album_ID=#Album_ID
The involved code is:
foreach (Database.MusicDBDataSet.TrackRow TR in this.trackTableAdapter1.GetAlbumTracks(AR.Artist_ID, AlR.Album_ID).Rows)
{
//if (!TR.FilePath.EndsWith(".mp3"))
//MessageBox.Show("File Path Error");
this.ArtistList[AR.Name].AlbumList[this.ArtistList[AR.Name].AlbumList.Count - 1].TrackList.Add(new Track(TR.FilePath, AlR.Name, AR.Name));
}
Has anyone ever run into this problem before?

Check the XSD file. Specifically, check the FilePath column of your table and look for the max length.

Maybe take a look at the SQLServerCE Parameter Size limitation.

What is the specific maximum length? Is it around 100 chars? (Guessing based on your provided input example).
The 100 unicode chars also matches with D.K. Mulligan's answer. Looking at SQL ServerCE Paramater Size Property
For variable-length data types, the Size property describes the maximum amount of data to send to the server. For example, the Size property can be used to limit the amount of data sent to the server for a string value to the first 100 bytes.
For Unicode string data, the Size property refers to the number of characters. The count for strings does not include the terminating character.
Try bumping the size to see if this is the magic number that is truncating your strings.