Question

I have a data table in SQL 2008 R2 which is used to store images. There is one column for uploaded image data whose SQL data type is “Image”

On the asp.NET layer I pull data into a dataset and then call GetXml() to get an XML string and then put the xml into a text file for import/export.

The image data is serialized into text but I can’t figure out how it’s encoded.

Original image data in the table: 0x89504E….
Image data in my XML string: iVBORw0KGgo…

I need to recover the String representation of the original 0x89504E…. and I assume that’s HEX. What encoding is the iVBORw0KGgo… ? I can’t find the info anywhere.

Answer 1

The encoding is base64.

The following code takes some binary data, puts it in a DataSet, runs GetXml(), and decodes the string in the XML as base64:

// Create a DataSet, DataTable, and define a binary column
DataSet dataSet = new DataSet("dataSet");
DataTable table = dataSet.Tables.Add("Items");
table.Columns.Add("image", typeof(byte[]));

/// Add one row of binary data (creating fake binary data from a string)
byte[] testData = new ASCIIEncoding().GetBytes("StackOverflow");
Console.WriteLine("Test data: " + new ASCIIEncoding().GetString(testData));
DataRow row = table.NewRow();
row["image"] = testData;
table.Rows.Add(row);

// Convert to XML and fetch the XML representation of the binary data
string xml = dataSet.GetXml();
XmlDocument doc = new XmlDocument();
doc.LoadXml(xml);
string xmlImageData = doc.SelectSingleNode("//image").InnerText;
Console.WriteLine("XML data: " + xmlImageData);

// base64decode the XML data and print its value
byte[] decoded = Convert.FromBase64String(xmlImageData);
Console.WriteLine("Decoded data: " + new ASCIIEncoding().GetString(decoded));

Output:

Test data: StackOverflow
XML data: U3RhY2tPdmVyZmxvdw==
Decoded data: StackOverflow