retrieve an image from a blob that has Base64String in asp.net c#

Question

I need help to get the string from a blob that has a Base64string that is uploaded and the image details saved in an mySql database by a client using a third party software. Here is the code i use to get the byte from the mysql database

byte[] imageByte =( byte[]) (dtImages.Rows[0]["fldData"]);

this is how i try to read it get into a string so that i can convert it back. It will not allow me to perform this conversion as it is a byte.

string image1Str = Convert.FromBase64String(imageByte);

How can i read the string from this to perform the conversion, once i have the string i can then save it as an image.

Koby Douek · Accepted Answer · 2017-04-24 05:27:37Z

1

Please try the following code.

Just replace the connection with your data connection, and replace <your query here> with the query to the BLOB object:

using System;
using System.Drawing;
using System.Collections;
using System.Data;
using System.Data.SqlClient;
using System.IO;

.... 

FileStream fs;                          // Writes the BLOB to a file.
BinaryWriter bw;                        // Streams the BLOB to the FileStream object.
int bufferSize = 100;                   // Size of the BLOB buffer.
byte[] outbyte = new byte[bufferSize];  // The BLOB byte[] buffer to be filled by GetBytes.
long retval;                            // The bytes returned from GetBytes.
long startIndex = 0;                    // The starting position in the BLOB output.

SqlDataReader myReader = connection.ExecuteReader(<your query here>);

while (myReader.Read())
{
    fs = new FileStream("my.bmp", FileMode.OpenOrCreate, FileAccess.Write);
    bw = new BinaryWriter(fs);
    startIndex = 0;
    retval = myReader.GetBytes(1, startIndex, outbyte, 0, bufferSize);

    while (retval == bufferSize)
    {
         bw.Write(outbyte);
         bw.Flush();
         startIndex += bufferSize;
         retval = myReader.GetBytes(1, startIndex, outbyte, 0, bufferSize);
    }

    bw.Write(outbyte, 0, (int)retval);
    bw.Flush();
    bw.Close();
    fs.Close();
}
myReader.Close();
connection.Close();

edited Apr 24, 2017 at 5:27

answered Apr 24, 2017 at 4:37

Koby Douek

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13 Comments

user1319463 Over a year ago

Thank-you for your timely reply., but when i try to put this code byte[] bytes = Convert.FromBase64String(dtImages.Rows[0]["fldData"]); getting a syntax error... cannot convert object to string

Koby Douek Over a year ago

What are the values in your database? Can you post an example of one of the values in dtImages.Rows[0]["fldData"] ?

user1319463 Over a year ago

the error is a syntax error... the blob is huge..unable to paste it

Koby Douek Over a year ago

What is the column fldData data type in the database? Blob ?

user1319463 Over a year ago

Koby, trying it...will let you know shortly.

|

Zephyr · Accepted Answer · 2017-04-24 05:00:17Z

0

Just my 2 cents, I think you should use Convert.ToBase64String instead of Convert.FromBase64String to get what you need.

More info at MSDN about

answered Apr 24, 2017 at 5:00

Zephyr

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