Cannot implicitly convert type 'long' to 'uint' and Use of unassigned local variable in C#

Question

I have an error "Cannot implicitly convert type 'long' to 'uint'. An explicit conversion exists (are you missing a cast?)" and "Use of unassigned local variable 'lASTINPUTINFO'"

Please Guide me

How can I solve the error and I am also a beginner in C# or There was something wrong in the implementation of the code I created or indeed the code I used was wrong

Thanks

The code below I use :

namespace Utilities
{
    internal class Win32
    {
        public Win32()
        {
        }

        public static uint GetIdleTime()
        {
            LASTINPUTINFO lASTINPUTINFO = new LASTINPUTINFO()
            {
`Error below line code Use of unassigned local variable`
                cbSize = (uint)Marshal.SizeOf<LASTINPUTINFO>(lASTINPUTINFO)
            };
            Win32.GetLastInputInfo(ref lASTINPUTINFO);
`Error below line code Cannot implicitly convert type long to uint`
            return Environment.TickCount - lASTINPUTINFO.dwTime;
        }

        [DllImport("Kernel32.dll", CharSet=CharSet.None, ExactSpelling=false)]
        private static extern uint GetLastError();

        [DllImport("User32.dll", CharSet=CharSet.None, ExactSpelling=false)]
        private static extern bool GetLastInputInfo(ref LASTINPUTINFO plii);

        public static long GetLastInputTime()
        {
            LASTINPUTINFO lASTINPUTINFO = new LASTINPUTINFO()
            {
`Error below line code Use of unassigned local variable`
                cbSize = (uint)Marshal.SizeOf<LASTINPUTINFO>(lASTINPUTINFO)
            };
            
    }
}

Answer 1

Thanks for @dr.null , @TinyWang , @Jimi problem solved

namespace Utilities
{
    internal class Win32
    {
        public Win32()
        {
        }
        public static uint GetIdleTime()
        {
            LASTINPUTINFO lASTINPUTINFO = new LASTINPUTINFO()
            {
                cbSize = (uint)Marshal.SizeOf<LASTINPUTINFO>()
            };
            Win32.GetLastInputInfo(ref lASTINPUTINFO);
            return (uint)Environment.TickCount - lASTINPUTINFO.dwTime;
        }

        [DllImport("Kernel32.dll", CharSet=CharSet.None, ExactSpelling=false)]
        private static extern uint GetLastError();

        [DllImport("User32.dll", CharSet=CharSet.None, ExactSpelling=false)]
        private static extern bool GetLastInputInfo(ref LASTINPUTINFO plii);

        public static long GetLastInputTime()
        {
            LASTINPUTINFO lASTINPUTINFO = new LASTINPUTINFO()
            {
                cbSize = (uint)Marshal.SizeOf<LASTINPUTINFO>()
            };
            if (!Win32.GetLastInputInfo(ref lASTINPUTINFO))
            {
                throw new Exception(Win32.GetLastError().ToString());
            }
            return (long)lASTINPUTINFO.dwTime;
        }

        public static long GetTickCount()
        {
            return (long)Environment.TickCount;
        }

        [DllImport("User32.dll", CharSet=CharSet.None, ExactSpelling=false)]
        public static extern bool LockWorkStation();
    }
}