Client Side Filtering

Once the data has been retrieved from the server, it can be filtered in the client without sending any requests to the server.

Open MainForm again in Designer mode and add a new textfield filterTextBox and a button applyFilterButton that will apply the filter.

Double click on the applyFilterButton to add the click event handler and then add the following code.

private void applyFilterButton_Click(object sender, EventArgs e)
{
  String filterText = this.filterTextBox.Text;

    if (String.IsNullOrEmpty(filterText))
    {
        this._dataSource.DataSource = this._data;
    }
    else
    {
        this._dataSource.DataSource = this._data.Where(task => task.Task.Contains(filterText) || task.Details.Contains(filterText));
    }
}

We first retrieve the text from the filterTextBox and test to see whether there is a value or not. If there isn't we show the original data again (effectively clearing the filter). Otherwise we create a new data source where elements match our filter text in either the task name or task description.

Run the app again

Enter some text in the filter text box, here we use "NoMatch" and the press the apply filter button. As you can see no match is found.

Change the text in the filter text box to something we know is in a task, here the text ID

The only thing left to do is summarize what we've done.