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FormViewDesigner.GetDesignTimeHtml Method

Gets the markup that is used to render the associated control at design time.

Namespace:  System.Web.UI.Design.WebControls
Assembly:  System.Design (in System.Design.dll)

public override string GetDesignTimeHtml()

Return Value

Type: System.String
A String containing the markup used to render the FormView at design time.

If an item template has been defined for the FormView control, the GetDesignTimeHtml method sets the DataKeyNames collection of the control to an empty String array if the schema for the data source cannot be obtained. The GetDesignTimeHtml refreshes the TypeDescriptor object to force a call to the PreFilterProperties method. The GetDesignTimeHtml then calls the base method to generate the markup.

If no item template has been defined for the FormView control, the GetDesignTimeHtml calls the GetEmptyDesignTimeHtml method to generate markup that renders to a placeholder.

Notes to Inheritors

If you override the GetDesignTimeHtml method, be sure to call the base method because it eventually, through several override levels, calls on the FormView control or a copy of the FormView control to generate the markup.

The following code example shows how to override the GetDesignTimeHtml method in a class that is inherited from the FormViewDesigner class to change the appearance of the FormView control at design time. The example adds a new first row to the grid to contain the Caption property, if the Caption is defined. If the BorderStyle property of the control that is derived from the FormView is the NotSet or None value, the GetDesignTimeHtml draws a blue dashed border around the control to make its extent more visible. The example does not change the run-time appearance of the control.

// Generate the design-time markup. 
const string capTag = "caption";
const string trOpen = "tr><td colspan=9 align=center";
const string trClose = "td></tr";

public override string GetDesignTimeHtml()
{
    // Make the full extent of the control more visible in the designer. 
    // If the border style is None or NotSet, change the border to 
    // a wide, blue, dashed line. Include the caption within the border.
    MyFormView myGV = (MyFormView)Component;
    string markup = null;
    int charX;

    // Check if the border style should be changed. 
    if (myGV.BorderStyle == BorderStyle.NotSet ||
        myGV.BorderStyle == BorderStyle.None)
    {
        BorderStyle oldBorderStyle = myGV.BorderStyle;
        Unit oldBorderWidth = myGV.BorderWidth;
        Color oldBorderColor = myGV.BorderColor;

        // Set the design-time properties and catch any exceptions. 
        try
        {
            myGV.BorderStyle = BorderStyle.Dashed;
            myGV.BorderWidth = Unit.Pixel(3);
            myGV.BorderColor = Color.Blue;

            // Call the base method to generate the markup.
            markup = base.GetDesignTimeHtml();
        }
        catch (Exception ex)
        {
            markup = GetErrorDesignTimeHtml(ex);
        }
        finally
        {
            // Restore the properties to their original settings.
            myGV.BorderStyle = oldBorderStyle;
            myGV.BorderWidth = oldBorderWidth;
            myGV.BorderColor = oldBorderColor;
        }
    }
    else 
        // Call the base method to generate the markup.
        markup = base.GetDesignTimeHtml();

    // Look for a <caption> tag. 
    if ((charX = markup.IndexOf(capTag)) > 0)
    {
        // Replace the first caption with  
        // "tr><td colspan=9 align=center".
        // It is okay if the colspan exceeds the  
        // number of columns in the table.
        markup = markup.Remove(charX,
            capTag.Length).Insert(charX, trOpen);

        // Replace the second caption with "td></tr".
        if ((charX = markup.IndexOf(capTag, charX)) > 0)
            markup = markup.Remove(charX,
                capTag.Length).Insert(charX, trClose);
    }
    return markup;

} // GetDesignTimeHtml

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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