检查上传文件的大小（以 mb 为单位）

Question

I need to verify that a file upload by a user does not exceed 10mb. Will this get the job done?

var fileSize = imageFile.ContentLength;
if ((fileSize * 131072) > 10)
{
    // image is too large
}

I've been looking at this thread , and this one ... but neither gets me all the way there. I'm using this as the conversion ratio.

.ContentLength gets the size in bytes. Then I need to convert it to mb.

Answer 1

Since you are given the size in bytes, you need to divide by 1048576 (ie 1024 * 1024 ):

var fileSize = imageFile.ContentLength;
if ((fileSize / 1048576.0) > 10)
{
    // image is too large
}

But the calculation is a bit easier to read if you pre-calculate the number of bytes in 10mb:

private const int TenMegaBytes = 10 * 1024 * 1024;


var fileSize = imageFile.ContentLength;
if ((fileSize > TenMegaBytes)
{
    // image is too large
}

Answer 2

You can use this method to convert the bytes you got to MB:

static double ConvertBytesToMegabytes(long bytes)
{
    return (bytes / 1024f) / 1024f;
}

Answer 3

Prefixes for multiples of bytes (B):
1024 bytes = 1kilobyte
1024 kilobyte = 1megabyte

double ConvertBytesToMegabytes(long bytes)
{
    return (bytes / 1024f) / 1024f;
} 

var fileSize = imageFile.ContentLength;

if (ConvertBytesToMegabytes(fileSize ) > 10f)
{
    // image is too large
}

Answer 4

var fileSize = file.ContentLength;
if (fileSize > 10 * 1024 * 1024)
{
    // Do whatever..
}