Get File Extension Using C#

private string getFileExtension(string fileName)
{

string extension=””;

char []arr=fileName.ToCharArray();

int index=0;

for(int i=0;i<arr.Length;i++)

{

if(arr[i]==’.’)

{

index=i;

}

}

for(int x=index+1;x<arr.Length;x++)

{

extension=extension+arr[x];

}

return extension;

}