C#

using System;
//using System.Linq;

static class Solution {
static int solution( int[] A ) {

    int flag = 1;
    //A = A.OrderBy(x => x).ToArray();
    Array.Sort(A);

        for (int i = 0; i < A.Length; i++)
        {
            if (A[i] <= 0)
            continue;
        else if (A[i] == flag)
        {
            flag++;
        }
    }
    return flag;
    }
    
    static void Main(string[] args) {
        
    int[] A = { 1, 3, 6, 4, 1, 2 }; 
    //int [] A ={1, 2, 3};
    //int [] A ={-1,-3};

        //var Val = A.Max();
       // if (Val < 1000000) {
        if(A.Length<99999)
        {
        int miss = solution(A);
        Console.Write(miss);       
        }
        else
        {
        Console.WriteLine(" Array is too large! ");
        }
        //}
        //else {
           // Console.WriteLine("Array Values are too big!");
        }
    }

Compiler output:
Compilation failed: 2 error(s), 0 warnings
exec.cs(18,24): error CS0017: Program `exec.exe' has more than one entry point defined: `SolutionWrapper.Main(string[])'
Solution.cs(23,17): error CS0017: Program `exec.exe' has more than one entry point defined: `Solution.Main(string[])'

Quote:

The local function 'Main' is declared but never used

<pre lang="C#"><pre>using System;
using System.Linq;

static int solution(int[] A) {
      int maxSize = 100000;
        int[] counter = new int[maxSize];

        foreach (var number in A)
        {
            if(number >0 && number <= maxSize)
            {
                counter[number - 1] = 1;
            }
        }

        for (int i = 0; i < maxSize; i++)
        {
            if (counter[i] == 0)
                return i + 1;
        }

        return maxSize + 1;    

    static void Main(string[] args) {
        
    int[] A = { 5, 9, 2, 7 };

    Console.WriteLine(solution(A));
    }
}

public async Task<List<Contact>> GetContactsAsync()
{
    return await this.dbContext.Contacts.ToListAsync();
}

class Program
{
    static void Main(string[] args)
    {
        Console.WriteLine("Calling Test()");
        Test();
        Console.WriteLine("After Test");

        Console.ReadLine();
    }

    private async static void Test()
    {
        Console.WriteLine("Calling GetSomeData()");
        var results = await GetSomeData();
        Console.WriteLine($"Results: {results}");
    }

    private static Task GetSomeData()
    {
        int x = 0;
        for (; x (x);
    }

    Thread.Sleep(5000);

    return Task.FromResult(x);
}

Calling Test()
Calling GetSomeData()
Results: 900000000
After Test

<ScrollViewer x:Name="Scroller" Grid.Row="2" Margin="0,0">
    <StackPanel>
        <ItemsControl x:Name="containers"
            ItemsSource="{Binding Whatever, NotifyOnTargetUpdated=True}"
            TargetUpdated="Containers_OnTargetUpdated">
        </ItemsControl>
    <StackPanel>
<ScrollViewer>

public partial class MyPage: UserControl
    {
        public MyPage()
        {
            InitializeComponent();
        }

        private void Containers_OnTargetUpdated(object? Sender, DataTransferEventArgs E)
        {
            var MyScroller = (ScrollViewer) this.FindName("Scroller");
            MyScroller.ScrollToHome();
        }
    }

private async Task SearchMostLessViewsAsync(DateTime dateFrom, DateTime dateTo, int amountOfNumbersSelected, int frequencyOption, int fromDrawNumber, int toDrawNumber)
        {
            Microsoft.AppCenter.Analytics.Analytics.TrackEvent($"{typeof(FragmentDrawsNumbersFrequency).Name}.{nameof(SearchMostLessViewsAsync)}",
                new Dictionary<string, string>()
                    {
                        {nameof(dateFrom), dateFrom.ToString()},
                        {nameof(dateTo), dateTo.ToString()},
                        {nameof(amountOfNumbersSelected), amountOfNumbersSelected.ToString()},
                        {nameof(frequencyOption), frequencyOption.ToString()},
                        {nameof(fromDrawNumber), fromDrawNumber.ToString()},
                        {nameof(toDrawNumber), toDrawNumber.ToString()},
                    }
                );
            ((MainActivity)Activity).DisplayLoadingMessage(true, GetString(Resource.String.Common_SearchTitle),
                GetString(Resource.String.Common_SearchMessage));

            //ApplicationState.ChangeCancellationTokenSource(new CancellationTokenSource());

            var task = Task.Run(async () =>
            {
                var textResult = await SearchLeast(dateFrom, dateTo, amountOfNumbersSelected, frequencyOption, fromDrawNumber, toDrawNumber).ConfigureAwait(false);

                if (!string.IsNullOrEmpty(textResult))
                {
                    UpdateHistoryList(textResult);
                    DatabaseFunctions.SaveHistoryList(HistoryList, Settings.DrawsNumbersFrequencyHistoryListViewKey);

                    ((MainActivity)Activity).ShowSearchResults(textResult);
                }
            }, ApplicationState.GetCancellationToken()); // Pass same token to Task.Run.

            try
            {
                await task.ConfigureAwait(false);
            }
            catch (TaskCanceledException tce)
            {
                Console.WriteLine($"{nameof(TaskCanceledException)} thrown with message: {tce.Message}");
            }
            catch (System.ObjectDisposedException ode)
            {
                Console.WriteLine($"{nameof(System.ObjectDisposedException)} thrown with message: {ode.Message}");
            }
            catch (System.OperationCanceledException e)
            {
                Console.WriteLine($"{nameof(System.OperationCanceledException)} thrown with message: {e.Message}");
            }
            catch (NullReferenceException nre)
            {
                Console.WriteLine($"{nameof(NullReferenceException)} thrown with message: {nre.Message}");
            }
            finally
            {
                ApplicationState.DisposeCancellationTokenSource();
                ((MainActivity)Activity).DisplayLoadingMessage(false);
            }

            ((MainActivity)Activity).DisplayLoadingMessage(false);
        }

FragmentDrawsNumbersFrequency.SearchMostLessViewsAsync (System.DateTime dateFrom, System.DateTime dateTo, System.Int32 amountOfNumbersSelected, System.Int32 frequencyOption, System.Int32 fromDrawNumber, System.Int32 toDrawNumber)
FragmentDrawsNumbersFrequency.ShowMostLessViews ()
FragmentDrawsNumbersFrequency.<OnCreateView>b__50_8 (System.Object sender, System.EventArgs e)
AsyncMethodBuilderCore+<>c.<ThrowAsync>b__7_0 (System.Object state)
SyncContext+<>c__DisplayClass2_0.<Post>b__0 ()
Thread+RunnableImplementor.Run ()
IRunnableInvoker.n_Run (System.IntPtr jnienv, System.IntPtr native__this)
(wrapper dynamic-method) Android.Runtime.DynamicMethodNameCounter.61(intptr,intptr)