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LINQ Challenges and SQL Server Compact Edition

, 25 Mar 2008 CPOL
Overcoming challenges with LINQ to SQL and using LINQ with SQL Server Compact Edition.
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 TimeApp.DataAccess;

namespace TimeApp.UI {

	public partial class ProjectForm : Form {

		// Fields.
		private Project CurrentProject;
		private bool IsProjectNew;
		private List<Task> ProjectTasks;

		public ProjectForm() {
			InitializeComponent();
		}

		public DialogResult ShowDialog(IWin32Window owner, Project project, bool isNew) {
			// Initialize fields and bind the data first.
			CurrentProject = project;
			IsProjectNew = isNew;
			ProjectTasks = new List<Task>(project.Tasks);
			BindData();

			return ShowDialog(owner);
		}

		public DialogResult ShowDialog(IWin32Window owner, Project project) {
			return ShowDialog(owner, project, false);
		}

		/// <summary>
		/// Binds the current project to the controls on the form.
		/// </summary>
		private void BindData() {
			// Fill the combobox with the estimation comparison types.
			cbEstimationComparisonType.DataSource = Enum.GetValues(typeof(EstimationComparisonType));
			cbEstimationComparisonType.SelectedIndex = -1;
			
			// Bind the controls to the data.
			txtName.DataBindings.Add("Text", CurrentProject, "Name");
			txtCode.DataBindings.Add("Text", CurrentProject, "Code");
			ctlEstimatedDuration.DataBindings.Add("Duration", CurrentProject, "EstimatedDuration", true, DataSourceUpdateMode.OnValidation, null);
			cbEstimationComparisonType.DataBindings.Add("SelectedItem", CurrentProject, "EstimationComparisonType", true, DataSourceUpdateMode.OnValidation, null);
			chkDetectAway.DataBindings.Add("Checked", CurrentProject, "DetectAway");
			chkIsBillable.DataBindings.Add("Checked", CurrentProject, "IsBillable");
			chkIsComplete.DataBindings.Add("Checked", CurrentProject, "IsComplete");

			// Bind to the tasks for the project.
			lbTasks.DataSource = ProjectTasks;
			lbTasks.DisplayMember = "Name";
			lbTasks.ValueMember = "TaskId";

			// Update the UI.
			Text = (IsProjectNew ? "New " : "Edit ") + Text;
			UpdateButtons();
		}

		private void RefreshTaskListData() {
			// Refresh the listbox's currency manager.
			CurrencyManager Manager = lbTasks.BindingContext[ProjectTasks] as CurrencyManager;
			Manager.Refresh();
		}

		/// <summary>
		/// Updates the buttons based on the state of the interface.
		/// </summary>
		private void UpdateButtons() {
			btnEdit.Enabled = (lbTasks.SelectedItem != null);
			btnDelete.Enabled = btnEdit.Enabled;
		}

		/// <summary>
		/// Opens a task form for adding a new task.
		/// </summary>
		private void AddTask() {
			// Create a new task for adding.
			Task TaskToAdd = new Task();
			TaskToAdd.Project = CurrentProject;

			// Show the task form.
			TaskForm frmTask = new TaskForm();
			if (frmTask.ShowDialog(this, TaskToAdd, true) != DialogResult.OK)
				// Disassociate the new task from the current project to discard it.
				TaskToAdd.Project = null;
			else {
				// Add the new task to the displayed list.
				ProjectTasks.Add(TaskToAdd);

				// Refresh the listbox's data.
				RefreshTaskListData();
			}
		}

		/// <summary>
		/// Opens a task form for editing the currently selected task.
		/// </summary>
		private void EditTask() {
			// Get the task for editing.
			Task TaskToEdit = (Task)lbTasks.SelectedItem;

			// Show the task form.
			TaskForm frmTask = new TaskForm();
			frmTask.ShowDialog(this, TaskToEdit);
		}

		/// <summary>
		/// Deletes the currently selected task.
		/// </summary>
		private void DeleteTask() {
			if (MessageBox.Show(this, "Delete this task?", "Delete Task", MessageBoxButtons.YesNo, MessageBoxIcon.Question) == DialogResult.Yes) {
				// Mark the task for deletion (if it is not new) and delete it from the displayed list.
				Task TaskToDelete = (Task)lbTasks.SelectedItem;
				if (TaskToDelete.TaskId > 0)
					TaskToDelete.IsMarked = true;
				ProjectTasks.Remove(TaskToDelete);

				// Refresh the listbox's data.
				RefreshTaskListData();
			}
		}

		private void lbTasks_SelectedIndexChanged(object sender, EventArgs e) {
			UpdateButtons();
		}

		private void lbTasks_DoubleClick(object sender, EventArgs e) {
			EditTask();
		}

		private void btnAdd_Click(object sender, EventArgs e) {
			AddTask();
		}

		private void btnEdit_Click(object sender, EventArgs e) {
			EditTask();
		}

		private void btnDelete_Click(object sender, EventArgs e) {
			DeleteTask();
		}

	}

}

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About the Author

Matt Sollars
Web Developer
United States United States
I began programming on my Commodore 64 at around the age of 12. After migrating to DOS and then Windows, I decided to take on the Web. Several languages and platforms later, I have settled in with .NET nicely. I am currently the owner of a software consulting company and lead application developer for a learning-based technology consultation company.
 
The love of a finished application is usually at war with the desire to improve it as soon as it's released (they're never really finished).

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