No problem in my codes, but i got this error.

Error 1 Unable to copy file "obj\Debug\WindowsFormsApplication3.exe" to ".\bin\Debug\WindowsFormsApplication3.exe". The process cannot access the file '.\bin\Debug\WindowsFormsApplication3.exe' because it is being used by another process. C:\Windows\Microsoft.NET\Framework\v4.0.30319\Microsoft.Common.targets 2869