Controlling Arduino with C#

[system]

I can identify the A, but how can i get the number xxx to be in int???

After determining that the first character in the array is indeed an 'A', replace the 'A' with a '0'. Then, call atoi() with the string as the argument.

char inData[] = "A382";
if(inData[0] == 'A')
{
   inData[0] = '0'; // inData now holds '0', '3', '8', '2', NULL

   int val = atoi(inData); // val now holds 382
}