Webカスタムコントロールの作成

/// <summary>
/// Writes out the HTML needed to render this control.
/// </summary>
/// <param name="output">The HTML text writer the we will utilize.
/// This is passed to the control automatically,
/// by the host ASPX page.</param>
protected override void Render(HtmlTextWriter output)
{
    try
    {
        // No need for ViewState
        this.EnableViewState = false;
        // Make sure that the htmlFieldName is set.
        GetHtmlFieldName();
        // Should the control be visible?
        if(this.Visible == true)
        {
             // Yes. Render the html.
             BuildCategorizedCheckBoxList(output);
        }
    }
    catch(Exception ex)
    {
        // Something bad happened. 
        // Let’s tell the user what that was.
        output.Write("Error building CategorizedCheckBoxList:<br>");
        output.Write(ex.Message);
    }
}

/// <summary>
/// Retrieves a list of the checkbox values that were
/// selected (checked), if the form was submitted.
/// This is kind of a poor-man’s view state implementation.
/// But unlike view state,
/// it doesn’t add anything to the page weight.
/// </summary>
protected void ReadPostBack()
{
    // See what field name we are assigning to the checkboxes
    GetHtmlFieldName();
    // Were any checkboxes checked?
    if(HttpContext.Current.Request.Form[htmlFieldName] != null)
    {
        // Since we assigned the same field name to all of
        // the checkboxes, ASP.NET will give us
        // a comma-delimited list of the selections.
        // First, conver the list to a string array.
        string [] Input = HttpContext.Current
            .Request.Form[htmlFieldName].Split(’,’);
        // Then, iterate through the array and add
        // each value to our ArrayList.
        for(int i = 0; i < Input.Length; i++)
        {
            selections.Add(Input[i]);
        }
    }
}

/// <summary>
/// Returns the unique field name
/// that we will assogn to the checkboxes, later.
/// </summary>
protected void GetHtmlFieldName()
{
    // Pickup the ID assigned to the control
    // in the consuming ASPX page
    htmlFieldName = this.ID;
}

/// <summary>
/// Outputs the HTML for this control.
/// </summary>
/// <param name="output"></param>
protected void BuildCategorizedCheckBoxList(HtmlTextWriter output)
{
    // Do we have any data?
    if(dataTable == null || dataTable.Rows.Count < 1)
    {
        // There is no data, so there’s nothing to render.
        return;
    }

// First retrieve the column indexes of
// the specified columns. Later, we’ll get
// the values that we need using these indexes.
// This is faster than referencing a column by name.
int CategoryColumnIndex = -1;
int TextColumnIndex = -1;
int ValueColumnIndex = -1;
for(int i = 0; i < dataTable.Columns.Count; i++)
{
    if(dataTextColumn == dataTable.Columns[i].ColumnName)
    {
        TextColumnIndex = i;
    }

    if(dataValueColumn == dataTable.Columns[i].ColumnName)
    {
        ValueColumnIndex = i;
    }
    if(dataCategoryColumn == dataTable.Columns[i].ColumnName)
    {
        CategoryColumnIndex = i;
    }
}

/**********************************/
/* Build the html to display of the items */
/**********************************/
// If the consuming page wants one single, shared table,
// write the opening tag, now.
if(this.sharedTable == true)
{
    output.Write(GetTableTag());
}

// Create a string for the "previous" category
string LastCategory = string.Empty;
// Sort the data by category
DataView Category = dataTable.DefaultView;
Category.Sort = this.dataCategoryColumn;
// Assemble a distinct list of the categories
// found in the data
ArrayList Categories = new ArrayList();
for(int i = 0; i < Category.Count; i++)
{
    if(LastCategory != Category[i][CategoryColumnIndex].ToString())
    {
        Categories.Add(Category[i][CategoryColumnIndex].ToString());
        LastCategory = Category[i][CategoryColumnIndex].ToString();
    }
}

// Loop through the categories
for(int i = 0; i < Categories.Count; i++)
{
    // Get the rows for this category only
    DataView CategoryItems = new DataView(dataTable);
    CategoryItems.RowFilter = String.Format("{0}=’{1}’",
        this.dataCategoryColumn,
        Categories[i].ToString().Replace("’","’’"));
    CategoryItems.Sort = this.dataTextColumn;

// If the consuming page wants a separate table
// for each category, write the opening tabel tag
// for the current category, now.
if(this.sharedTable == false)
{
     output.Write(GetTableTag());
}

// Add the category heading to the html
OutputCategoryRow(output, (string)Categories[i]);

// Calculate the total number of rows based on
// the item count and the number of columns
totalItems = CategoryItems.Count;
totalRows = totalItems / columns;
// If there was anything left-over as a result of
// the division, we need to add another row
if(totalItems % columns > 0)
{
    totalRows++;
}

// Create an integer to hold the index number
// for the current item
int CurrentItemIndex = 0;
// Now loop through the rows
for(int Row = 0; Row < totalRows; Row++)
{
    // Determine the starting index for this row.
    // This is the same calculation that we would perform
    // to handle paging in a grid.
    int Start = (Row * columns);
    // Create an integer to hold the index number
    // for the current item
    int CurrentItemIndex = Start;
    // Start the row
    output.Write("");
    output.Write("<tr class="");
    output.Write(this.rowCssClass);
    output.Write("">");
    output.Write("
");
    // Column loop
    for(int Col = 0; Col < columns; Col++)
    {
        // Make sure that we haven’t hit a blank entry.
        if(CurrentItemIndex == -1)
        {
            // Add an empty cell (two, actually)
            AddEmptyCells(output);
        }
        else
        {
            // Now add the checkbox and text
            OutputCheckBox(output,
                htmlFieldName,
                CategoryItems[CurrentItemIndex]
                    [TextColumnIndex].ToString(),
                CategoryItems[CurrentItemIndex]
                    [ValueColumnIndex].ToString(),
                IsChecked(CategoryItems[CurrentItemIndex]
                    [ValueColumnIndex].ToString())
                );
            // If we have more data left,
            // increment the current index counter.
            if(CurrentItemIndex < (totalItems - 1)
                && CurrentItemIndex != -1)
            {
                // increment the current index
                CurrentItemIndex++;
            }
            else
            {
                // We’re at the end of the items
                // in the data table. Set the value of
                // the current index to -1,
                // which our rendering code
                // ignores (creates empty table cells)
                CurrentItemIndex = -1;
            }
        }
        // Add a line break
        output.Write("
");
    }

    // End the row
    output.Write("");
    output.Write("</tr>
");
}

    // Table tag
    if(this.sharedTable == false)
    {
        output.Write("</table>
");
    }
}

    // Finish the table
    if(this.sharedTable == true)
    {
        output.Write("</table>
");
    }

    /**********************************/
}

/// <summary>
/// Looks for a match between the current value and
/// the list of selected values.
/// </summary>
/// <param name="currentValue">The value that we want to look for.
/// </param>
/// <returns>True if the current value is contained in
/// the selected list. Otherwise, false.</returns>
protected bool IsChecked(string currentValue)
{
    // If we have selections, continue
    if(selections != null && selections.Count > 0)
    {
        // Can we find the current value?
        if(selections.IndexOf(currentValue) > -1)
        {
            // Yes, so this item should be marked
            // as selected (checked)
            return true;
        }
        else
        {
            // No, so this item should not be selected
            return false;
        }
    }
    else
    {
        // Nothing at all was selected, so return false
        return false;
    }
}

[Category("Appearance"),
DefaultValue(""),
Description("The CSS Class name for the table row" 
    + "containing each item.")]
public string RowCssClass
{

/// <summary>
/// Provides a moderate level of fidelity
/// for the CategorizedCheckBoxList control
/// in the VS.net IDE.
/// </summary>
internal class CategorizedCheckBoxListControlDesigner :
    System.Web.UI.Design.ControlDesigner
{
    /// <summary>
    /// Provides easy access the properties set in the IDE.
    /// </summary>
    protected CategorizedCheckBoxList ccbl;
    /// <summary>
    /// Initializes the designer
    /// </summary>
    /// <param name="component"></param>
    public override void Initialize(IComponent component)
    {
        // Make sure that this designer is attached to
        // a CategorizedCheckBoxList
        if(component is CategorizedCheckBoxList)
        {
            base.Initialize (component);
            ccbl = (CategorizedCheckBoxList)component;
        }
    }

/// <summary>
/// Writes the HTML used be VS.net to display
/// the control at design-time.
/// </summary>
/// <returns></returns>
public override string GetDesignTimeHtml()
{
    try
    {
        // Start building the HTML
        StringBuilder Sb = new StringBuilder();

        // Table
        Sb.Append("<table");
        Sb.Append(" cellspacing="");
        Sb.Append(ccbl.CellSpacing.ToString());
        Sb.Append(""");
        Sb.Append(" cellpadding="");
        Sb.Append(ccbl.CellPadding.ToString());
        Sb.Append(""");
        Sb.Append(" border="0">");
        // Category Row
        Sb.Append("<tr><td colspan="4"");
        Sb.Append(" class="");
        Sb.Append(ccbl.CategoryCssClass);
        Sb.Append(""");
        Sb.Append(">Fruit</td></tr>");
        // Item Row
        Sb.Append("<tr valign="top">");
        Sb.Append("<td><input type="checkbox" "
            + "name="1" value="1" class="");
        Sb.Append(ccbl.CheckBoxCssClass);
        Sb.Append(""></td>");
        Sb.Append("<td class="");
        Sb.Append(ccbl.TextCssClass);
        Sb.Append("">Apples</td>");
        Sb.Append("<td><input type="checkbox" "
            + "name="1" value="2" class="");
        Sb.Append(ccbl.CheckBoxCssClass);
        Sb.Append(""></td>");
        Sb.Append("<td class="");
        Sb.Append(ccbl.TextCssClass);
        Sb.Append("">Oranges</td>");
        Sb.Append("</tr>");
        // Item Row
        Sb.Append("<tr valign="top">");
        Sb.Append("<td><input type="checkbox" "
            + "name="1" value="3" class="");
        Sb.Append(ccbl.CheckBoxCssClass);
        Sb.Append(""></td>");
        Sb.Append("<td class="");
        Sb.Append(ccbl.TextCssClass);
        Sb.Append("">Tangerines</td>");
        Sb.Append("<td></td>");
        Sb.Append("<td class="");
        Sb.Append(ccbl.TextCssClass);
        Sb.Append(""></td>");
        Sb.Append("</tr>");
        // Category Row
        Sb.Append("<tr><td colspan="4"");
        Sb.Append(" class="");
        Sb.Append(ccbl.CategoryCssClass);
        Sb.Append(""");
        Sb.Append(">Vegetables</td></tr>");
        // Item Row
        Sb.Append("<tr valign="top">");
        Sb.Append("<td><input type="checkbox" "
            + "name="2" value="1" class="");
        Sb.Append(ccbl.CheckBoxCssClass);
        Sb.Append(""></td>");
        Sb.Append("<td class="");
        Sb.Append(ccbl.TextCssClass);
        Sb.Append("">Broccoli</td>");
        Sb.Append("<td><input type="checkbox" "
            + "name="2" value="2" class="");
        Sb.Append(ccbl.CheckBoxCssClass);
        Sb.Append(""></td>");
        Sb.Append("<td class="");
        Sb.Append(ccbl.TextCssClass);
        Sb.Append("">Green Beans</td>");
        Sb.Append("</tr>");
        // Item Row
        Sb.Append("<tr valign="top">");
        Sb.Append("<td><input type="checkbox" "
            + "name="2" value="3" class="");
        Sb.Append(ccbl.CheckBoxCssClass);
        Sb.Append(""></td>");
        Sb.Append("<td class="");
        Sb.Append(ccbl.TextCssClass);
        Sb.Append("">Potatoes</td>");
        Sb.Append("<td><input type="checkbox" "
            + "name="2" value="4" class="");
        Sb.Append(ccbl.CheckBoxCssClass);
        Sb.Append(""></td>");
        Sb.Append("<td class="");
        Sb.Append(ccbl.TextCssClass);
        Sb.Append("">Tomatoes</td>");
        Sb.Append("</tr>");
        // End the table
        Sb.Append("</table>");
        return Sb.ToString();
    }
    catch(Exception ex)
    {
        // Display the error in VS.net, in Design view
        return String
            .Concat("<h3>Error</h3>Stack Trace:<br>", ex.StackTrace);
    }
}

/// <summary>
/// The CategorizedCheckBoxList is like a CheckBoxList,
/// but with the ability to categorize the display of items.
/// </summary>
[Designer(
"UsefulControls.CategorizedCheckBoxListControlDesigner"),
DefaultProperty("DataTable"),
ToolboxData("<{0}:ccbl runat=server></{0}:ccbl>")]
public class CategorizedCheckBoxList :
    System.Web.UI.WebControls.WebControl
{
    /// <summary>
    /// Initializes a new instance of
    /// the CategorizedCheckBoxList class.
    /// </summary>
    public CategorizedCheckBoxList()
    {
        // Init the class
    }

private void Page_Load(object sender, System.EventArgs e)
{
    // If the page has not posted-back,
    // or if it has but the "Show List" checkbox is checked,
    // get the data for our CategorizedCheckBoxList.
    if(!IsPostBack || chkShowList.Checked == true)
    {
        // Get the data
        GetMdbData();
    }
    else
    {
        // Hide the CategorizedCheckBoxList
        CategorizedCheckBoxList1.Visible = false;
        // Hide the "Show List" checkbox
        chkShowList.Visible = false;
        // Hide the submit button, too
        btnTestValues.Visible = false;
    }
}

protected void GetMdbData()
{
    // Create a connetion
    OleDbConnection Conn = new OleDbConnection();
    Conn.ConnectionString = String.Concat(
        "Provider=Microsoft.Jet.OleDb.4.0;data source=",
        Server.MapPath("SampleData.mdb"));
    // Build a data adapter that selects all of the columns
    // and rows in a saved query called qryCarModelCarMaker,
    // in the Access database
    OleDbDataAdapter Adp = new OleDbDataAdapter(
        "SELECT * FROM qryCarModelCarMaker", Conn);

    // Create an instance of our Cars typed dataset
    Cars TypedSampleData = new Cars();
    // Use the adapter to fill the CarTable
    Adp.Fill(TypedSampleData, "CarTable");
    // Specify the data properties for
    // our CategorizedCheckBoxList control
    CategorizedCheckBoxList1.DataTable = TypedSampleData.CarTable;
    CategorizedCheckBoxList1.DataTextColumn = "Model";
    CategorizedCheckBoxList1.DataValueColumn = "CarModelPK";
    CategorizedCheckBoxList1.DataCategoryColumn = "Make";
    // Clean-up
    Conn.Dispose();
    Adp.Dispose();
}

private void btnTestValues_Click(object sender, System.EventArgs e)
{
    // Were any checkboxes checked?
    if(CategorizedCheckBoxList1.Selections.Count > 0)
    {
        // Yes. Let’s use a string builder to tell
        // the user what we find.
        StringBuilder Sb = new StringBuilder();
        Sb.Append("The following values were selected:");
        
        // Use an HTML un-ordered list to display the values
        Sb.Append("<ul>");

        // Loop through the selections
        foreach(string check in CategorizedCheckBoxList1.Selections)
        {
             // Add this item to our HTML list
             Sb.Append("<li>");
             Sb.Append(check);
             Sb.Append("</li>");
        }
        // End the list
        Sb.Append("</ul>");
        // Set the text of our label
        Label1.Text = Sb.ToString();
    }
    else
    {
        // Use our label to tell the user
        // that nothing was picked.
        Label1.Text = "No checkboxes were selected.";
    }
}

// If the page has not posted-back,
// or if it has but the "Show List" checkbox is checked,
// get the data for our CategorizedCheckBoxList.
if(!IsPostBack || chkShowList.Checked == true)
{
    // Get the data
    GetMdbData();
    // Select all of the Audi models
    CategorizedCheckBoxList1.Selections.Add("37");
    CategorizedCheckBoxList1.Selections.Add("38");
    CategorizedCheckBoxList1.Selections.Add("39");
    CategorizedCheckBoxList1.Selections.Add("40");
    CategorizedCheckBoxList1.Selections.Add("41");
}