.NET (Core and Framework)

<Window x:Class="InputTaskQueue.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:behav="clr-namespace:InputTaskQueue.Behaviors"
        mc:Ignorable="d"
        Title="MainWindow" Height="350" Width="525">
    <StackPanel Orientation="Vertical">
        <TextBox Name="tbInput"
                 behav:TextChangedCommand.ChangedCommand="{Binding SearchCommand}"
                 HorizontalAlignment="Left" VerticalAlignment="Bottom"
                 Width="100" Height="20"/>

        <TextBlock Text="{Binding SearchStringResult,UpdateSourceTrigger=PropertyChanged,Mode=OneWay}" Width="100" Height="100" />
    </StackPanel>
</Window>

using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;

public static class TextChangedCommand
{
    // Field of attached ICommand property
    private static readonly DependencyProperty ChangedCommandProperty = DependencyProperty.RegisterAttached(
        "ChangedCommand",
        typeof(ICommand),
        typeof(TextChangedCommand),
        new PropertyMetadata(null, OnTextChangedCommandChange));

    public static void SetChangedCommand(DependencyObject source, ICommand value)
    {
        source.SetValue(ChangedCommandProperty, value);
    }

    public static ICommand GetChangedCommand(DependencyObject source)
    {
        return (ICommand)source.GetValue(ChangedCommandProperty);
    }

    private static void OnTextChangedCommandChange(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        TextBox uiElement = d as TextBox;   // Remove the handler if it exist to avoid memory leaks

        if (uiElement != null)
        {
            uiElement.TextChanged -= OnText_Changed;

            var command = e.NewValue as ICommand;
            if (command != null)
            {
                // the property is attached so we attach the Drop event handler
                uiElement.TextChanged += OnText_Changed;
            }
        }
    }

    private static void OnText_Changed(object sender, TextChangedEventArgs e)
    {
        TextBox uiElement = sender as TextBox;

        // Sanity check just in case this was somehow send by something else
        if (uiElement == null)
            return;

        // Bugfix: A change during disabled state is likely to be caused by a bound property
        //         in a viewmodel (a machine based edit rather than user input)
        //         -> Lets break the message loop here to avoid unnecessary CPU processings...
        if (uiElement.IsEnabled == false)
            return;

        ICommand changedCommand = TextChangedCommand.GetChangedCommand(uiElement);

        // There may not be a command bound to this after all
        if (changedCommand == null)
            return;

        var item = uiElement.Text;

        // Check whether this attached behaviour is bound to a RoutedCommand
        if (changedCommand is RoutedCommand)
        {
            // Execute the routed command
            (changedCommand as RoutedCommand).Execute(item, uiElement);
        }
        else
        {
            // Execute the Command as bound delegate
            changedCommand.Execute(item);
        }
    }
}

private string _SearchStrinResult;

/// <summary>
/// Gets a search string to match in the tree view.
/// </summary>
public string SearchStringResult
{
    get { return _SearchStrinResult; }
    private set
    {
        if (_SearchStrinResult != value)
        {
            _SearchStrinResult = value;
            NotifyPropertyChanged(() => SearchStringResult);
        }
    }
}
#endregion properties

#region methods
/// <summary>
/// Gets a command that filters the display of nodes in a treeview
/// with a filterstring (node is shown if filterstring is contained).
/// </summary>
public ICommand SearchCommand
{
    get
    {
        if (_SearchCommand == null)
        {
            _SearchCommand = new RelayCommand<object>((p) =>
            {
                string findThis = p as string;

                if (string.IsNullOrEmpty(findThis) == true)
                    return;

                SearchCommand_ExecutedAsync(findThis);
            },
            (p =>
            {
                return true;
            })
            );
        }

        return _SearchCommand;
    }
}

private List<string> _Queue = new List<string>();
private static SemaphoreSlim SlowStuffSemaphore = new SemaphoreSlim(1, 1);

private async void SearchCommand_ExecutedAsync(string input)
{
    _Queue.Add(input);

    // Issue 1: Not sure how to lock this with the correct semaphore信号
    //to make sure the task always processes the last input but is not started twice
    await SlowStuffSemaphore.WaitAsync();
    try
    {
        // There is more recent input to process so we ignore this one
        if (_Queue.Count > 1)
        {
            _Queue.Remove(input);
            return;
        }
        else
        {
            Console.WriteLine("Queue Count: {0}", _Queue.Count);
        }

        await createTask(input);

        _Queue.Remove(input);

        this.SearchStringResult = input;
    }
    catch (Exception exp)
    {
        Console.WriteLine(exp.Message);
    }
    finally
    {
        SlowStuffSemaphore.Release();
    }
}

private Task createTask(string input)
{
    return Task.Run(() =>
    {
        Console.WriteLine("searching:" + input);
        System.Threading.Thread.Sleep(5000);

    }) // simulate processing
    .ContinueWith((p) =>
    {
    });
}

An unhandled exception of type 'System.AccessViolationException' occurred in System.Data.dll

Additional information: Attempted to read or write protected memory. This is often an indication that other memory is corrupt. 

        public static string ConvertXlsAndXlstToPipeDelimitedFile(string strSourceFilePath, bool isFirstRowColumnHeader, string sheetName)
        {
            string strConn = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" +
                strSourceFilePath + ";Extended Properties=\"Excel 8.0;HDR=Yes;IMEX=1\"";

            OleDbConnection conn = null;
            StreamWriter wrtr = null;
            OleDbCommand cmd = null;
            OleDbDataAdapter da = null;

            string destinationFilePath = string.Empty;

            conn = new OleDbConnection(strConn);           

            try
            {
                if (conn.State != ConnectionState.Open)
                {
                    conn.Open();
                }

                cmd = new OleDbCommand("SELECT * FROM [" + sheetName + "$]", conn); //"Sheet1"
                cmd.CommandType = CommandType.Text;

                da = new OleDbDataAdapter(cmd);
                DataTable dt = new DataTable();
                da.Fill(dt);

                string strDirectory = (System.IO.Path.GetDirectoryName(strSourceFilePath));

                if (!System.IO.Directory.Exists(strDirectory))
                {
                    System.IO.Directory.CreateDirectory(strDirectory);
                }

                Path.GetFileNameWithoutExtension(strSourceFilePath);

                destinationFilePath = (strDirectory + (@"\" + (Path.GetFileNameWithoutExtension(strSourceFilePath) + ".csv")));

                wrtr = new StreamWriter(destinationFilePath);

                int ColCount = 0; string rowString = "";
                for (int y = 0; y < dt.Columns.Count; y++)
                {
                    rowString += dt.Columns[y].ColumnName + "|";

                }
                wrtr.WriteLine(rowString);

                for (int x = 0; x < dt.Rows.Count; x++)
                {
                    rowString = "";
                    for (int y = 0; y < dt.Columns.Count; y++)
                    {
                        rowString += "\"" + dt.Rows[x][y].ToString() + "\"|";
                    }
                    wrtr.WriteLine(rowString);
                }

                if (File.Exists(destinationFilePath))
                    return destinationFilePath;
            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally
            {
                if (conn != null)
                {
                    if (conn.State != ConnectionState.Closed)
                    {
                        conn.Close();
                    }
                    conn.Dispose();
                }

                if (cmd != null)
                {
                    cmd.Dispose();
                }
                if (da != null)
                {
                    da.Dispose();
                }

                if (wrtr != null)
                {
                    wrtr.Close();
                    wrtr.Dispose();
                }
            }
            //MessageBox.Show("Done");
            return string.Empty;
        }

Error: 0xC0049064 at Populate Stage, Derived Column [97]: An error occurred while attempting to perform a type cast.
Error: 0xC0209029 at Populate Stage, Derived Column [97]: SSIS Error Code DTS_E_INDUCEDTRANSFORMFAILUREONERROR.  The "Derived Column" failed because error code 0xC0049064 occurred, and the error row disposition on "Derived Column.Outputs[Derived Column Output].Columns[Payment Due Date]" specifies failure on error. An error occurred on the specified object of the specified component.  There may be error messages posted before this with more information about the failure.
Error: 0xC0047022 at Populate Stage, SSIS.Pipeline: SSIS Error Code DTS_E_PROCESSINPUTFAILED.  The ProcessInput method on component "Derived Column" (97) 
failed with error code 0xC0209029 while processing input "Derived Column Input" (98). The identified component returned an error from the ProcessInput method. 

The error is specific to the component, but the error is fatal and will cause the Data Flow task to stop running.  There may be error messages posted before this with more information about the failure.

(DT_DATE)(SUBSTRING([Date Posted],1,4) + "-" + SUBSTRING([Date Posted],5,2) + "-" + SUBSTRING([Date Posted],7,2))