C#で画面の輝度を変更するプログラムの作成時の質問です

Question

VisualStudio2013にてC#を利用して画面の輝度を変更するプログラムを作成しています。
そのためにサンプルプログラムを見つけ実行したのですがうまく動作しません。

エラーメッセージ
なし
問題
画面の輝度が変わるはずなのに画面が変化せずformが起動しただけになっている。
またbool SetACBrightnessを呼び出し値を入れる方法がわからない。

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;
using System.Drawing.Imaging;
using System.Globalization;
using Microsoft.Win32;

namespace WindowsFormsApplication3
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        #region Constants
        /// <summary>
        /// Settings in this subgroup control configuration of the video power management features.
        /// </summary>
        public Guid GUID_VIDEO_SUBGROUP = new Guid("7516b95f-f776-4464-8c53-06167f40cc99");

        /// <summary>
        /// Guid for display brightness setting.
        /// </summary>
        public Guid DisplayBrightnessGuid = new Guid("aded5e82-b909-4619-9949-f5d71dac0bcb");
        #endregion

        #region Methods
        /// <summary>
        /// Retrieves the AC index of the specified power setting.
        /// </summary>
        /// <param name="RootPowerKey">This parameter is reserved for future use and must be set to NULL.</param>
        /// <param name="SchemeGuid">The identifier of the power scheme.</param>
        /// <param name="SubGroupOfPowerSettingsGuid">The subgroup of power settings. This parameter can be one of the following values defined in WinNT.h. Use NO_SUBGROUP_GUID to refer to the default power scheme.</param>
        /// <param name="PowerSettingGuid">The identifier of the power setting</param>
        /// <param name="AcValueIndex">A pointer to a variable that receives the AC value index.</param>
        /// <returns>Returns ERROR_SUCCESS (zero) if the call was successful, and a nonzero value if the call failed.</returns>
        [DllImport("powrprof.dll", EntryPoint = "PowerReadACValueIndex", CharSet = CharSet.Auto, SetLastError = true)]
        public static extern uint PowerReadACValueIndex(IntPtr RootPowerKey, ref Guid SchemeGuid, ref Guid SubGroupOfPowerSettingsGuid, ref Guid PowerSettingGuid, out uint AcValueIndex);


        /// <summary>
        /// Sets the AC value index of the specified power setting.
        /// </summary>
        /// <param name="RootPowerKey">This parameter is reserved for future use and must be set to NULL.</param>
        /// <param name="SchemeGuid">The identifier of the power scheme.</param>
        /// <param name="SubGroupOfPowerSettingsGuid">The subgroup of power settings. This parameter can be one of the following values defined in WinNT.h. Use NO_SUBGROUP_GUID to refer to the default power scheme.</param>
        /// <param name="PowerSettingGuid">The identifier of the power setting</param>
        /// <param name="AcValueIndex">The AC value index.</param>
        /// <returns>Returns ERROR_SUCCESS (zero) if the call was successful, and a nonzero value if the call failed.</returns>
        [DllImport("powrprof.dll", EntryPoint = "PowerWriteACValueIndex", CharSet = CharSet.Auto, SetLastError = true)]
        public static extern uint PowerWriteACValueIndex(IntPtr RootPowerKey, ref Guid SchemeGuid, ref Guid SubGroupOfPowerSettingsGuid, ref Guid PowerSettingGuid, uint AcValueIndex);

        /// <summary>
        /// Retrieves the AC index of the specified power setting.
        /// </summary>
        /// <param name="RootPowerKey">This parameter is reserved for future use and must be set to NULL.</param>
        /// <param name="SchemeGuid">The identifier of the power scheme.</param>
        /// <param name="SubGroupOfPowerSettingsGuid">The subgroup of power settings. This parameter can be one of the following values defined in WinNT.h. Use NO_SUBGROUP_GUID to refer to the default power scheme.</param>
        /// <param name="PowerSettingGuid">The identifier of the power setting</param>
        /// <param name="AcValueIndex">A pointer to a variable that receives the AC value index.</param>
        /// <returns>Returns ERROR_SUCCESS (zero) if the call was successful, and a nonzero value if the call failed.</returns>
        [DllImport("powrprof.dll", EntryPoint = "PowerReadDCValueIndex", CharSet = CharSet.Auto, SetLastError = true)]
        public static extern uint PowerReadDCValueIndex(IntPtr RootPowerKey, ref Guid SchemeGuid, ref Guid SubGroupOfPowerSettingsGuid, ref Guid PowerSettingGuid, out uint AcValueIndex);


        /// <summary>
        /// Sets the AC value index of the specified power setting.
        /// </summary>
        /// <param name="RootPowerKey">This parameter is reserved for future use and must be set to NULL.</param>
        /// <param name="SchemeGuid">The identifier of the power scheme.</param>
        /// <param name="SubGroupOfPowerSettingsGuid">The subgroup of power settings. This parameter can be one of the following values defined in WinNT.h. Use NO_SUBGROUP_GUID to refer to the default power scheme.</param>
        /// <param name="PowerSettingGuid">The identifier of the power setting</param>
        /// <param name="AcValueIndex">The AC value index.</param>
        /// <returns>Returns ERROR_SUCCESS (zero) if the call was successful, and a nonzero value if the call failed.</returns>
        [DllImport("powrprof.dll", EntryPoint = "PowerWriteDCValueIndex", CharSet = CharSet.Auto, SetLastError = true)]
        public static extern uint PowerWriteDCValueIndex(IntPtr RootPowerKey, ref Guid SchemeGuid, ref Guid SubGroupOfPowerSettingsGuid, ref Guid PowerSettingGuid, uint AcValueIndex);


        /// <summary>
        /// Sets the active power scheme for the current user.
        /// </summary>
        /// <param name="UserRootPowerKey">This parameter is reserved for future use and must be set to NULL.</param>
        /// <param name="SchemeGuid">The identifier of the power scheme.</param>
        /// <returns>Returns ERROR_SUCCESS (zero) if the call was successful, and a nonzero value if the call failed.</returns>
        [DllImport("powrprof.dll", EntryPoint = "PowerSetActiveScheme", CharSet = CharSet.Auto, SetLastError = true)]
        public static extern uint PowerSetActiveScheme(IntPtr UserRootPowerKey, ref Guid SchemeGuid);

        #endregion

        Guid MY_POWER_MANAGEMENT_POLICY = new Guid("8c5e7fda-e8bf-4a96-9a85-a6e23a8c635c"); // 今回は<SCHEME_GUID>をベタ指定
        //381b4222-f694-41f0-9685-ff5bb260df2e(バランス)
        //8c5e7fda-e8bf-4a96-9a85-a6e23a8c635c(高パフォーマンス)
        //a1841308-3541-4fab-bc81-f71556f20b4a(省電力)


       

        bool SetACBrightness(int bright_ac){
                                                                                      
	        if(bright_ac < 0 || bright_ac > 100)
		    return false;

	        uint ret = PowerWriteACValueIndex(IntPtr.Zero, ref MY_POWER_MANAGEMENT_POLICY, ref GUID_VIDEO_SUBGROUP, ref DisplayBrightnessGuid, (uint)bright_ac);
	        if(ret != 0)
		    return false;

	        ret = PowerSetActiveScheme(IntPtr.Zero, ref MY_POWER_MANAGEMENT_POLICY);
	        if(ret != 0)
		    return false;

	        return true;
        }
   
     
   }

        
}

#試したこと
bool SetACBrightnessの前にint SetACBrightnessを設定し値を代入したのですがbool SetACBrightnessにて定義されていると言われました。そのため実行ができませんでした。

Answer 1

buttonをformにて作成し、
buttonをクリックしたら画面の明るさを変更するようにしたらうまく実行できました。

また画面の明るさを徐々に変化させるプログラムを追記します。

private void button1_Click_1(object sender, EventArgs e)
 {
 //徐々にスクリーンの明るさの変更を行うソースコード
            int c_ac = 1;
            for (int i = 100; i >1; i--)
            {
                c_ac = i;

                //boolの実行
                if (SetACBrightness(c_ac) == true)
                {
                }
            }
            for (int i = 0; i <= 100; i++)
            {
                c_ac = i;
                //boolの実行
                if (SetACBrightness(c_ac) == true)
                {
                }
            }
}

Answer 2

SetACBrightnessの呼び出し方と言われても、まず「いつ呼び出すか」、「引数のbright_acの値をどうやって決定するか」を決めてください。
これはプログラムを作成する貴方が決定することであり、これが決まらないと呼び出し方も決定しません。