cannot convert from 'ref byte[]' to 'ref object'

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I try to read the pixels value on a line in an image:

C#

byte[] myArray=new byte[20];
for(int i=0;i<20;i++)
    myArray[i]=0;

myImage.GetLine(ref myArray, 10,10,20,10);

Getline is the function provided by myImage, which has 5 parameters:
ref object, int startX,int startY, int endX,int EndY;

When run the above code, it will show error as: cannot convert 'ref byte[]' to 'ref object'.

But when I call it in this way:

C#

object points=null;
myImage.GetLine(ref points,10,10,20,10);
The error will show as: invalid userarray.

Don't know why?

Posted 26-Aug-13 22:42pm

yuzaihuan

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2 solutions

Solution 2

Seems it will need a cast from myArray to Object.
What I want to get is to get a pixel's value when mouse moved on an image.

Thank you. I will try this later.

Posted 27-Aug-13 21:20pm

yuzaihuan

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OriginalGriff · Accepted Answer · 2013-08-26T22:53:00

You cannot call the method with a ref parameter to any type other than exactly the parameter type specified. The reasoning is pretty simple - suppose you could:

C#

private void MyMethod(ref object o)
   {
   o = (object) new Point(10, 10);
   }
...
   byte[] data = new byte[1024];
   MyMethod(ref data);
   Console.WriteLine(data[100]);

What kind of output would you get? Apart from random and rubbish?

In order to call a method with a ref parameter, it must be an assignable value, so try

C#

byte[] myArray=new byte[20];
for(int i=0;i<20;i++)
    myArray[i]=0;
object o = myArray;
myImage.GetLine(ref o, 10,10,20,10);

The method can then change the value of o without affecting the array in any way.