Customize rendering of custom field types

Question

How can I customize rendering of a custom field type in SharePoint using server side code?

I searched on the net but I am getting examples with csr technology i.e. JSLink. I want to know how I can do it in another way.

I want my field to have a default value or placeholder when displayed in new form for a list or library.

Answer 1

Setting default values for custom field types is only possible in changing the implementation on server side.

Check out this nice MSDN walkthrough regarding the implementation of custom field types.

The sample explains also how to set a default value.

protected override void CreateChildControls()
{
    if (this.Field != null)
    {
        // Make sure inherited child controls are completely rendered.
        base.CreateChildControls();

        // Associate child controls in the .ascx file with the 
        // fields allocated by this control.
        this.ISBNPrefix = (Label)TemplateContainer.FindControl("ISBNPrefix");
        this.textBox = (TextBox)TemplateContainer.FindControl("TextField");
        this.ISBNValueForDisplay = (Label)TemplateContainer.FindControl("ISBNValueForDisplay");

        if (this.ControlMode != SPControlMode.Display)
        {
            if (!this.Page.IsPostBack)
            {
                if (this.ControlMode == SPControlMode.New)
                {
                    // setting default value here!
                    textBox.Text = "0-000-00000-0";
                }
             }
        }
        else
        {                 
            // Assign current value from database to the label control
            ISBNValueForDisplay.Text = (String)this.ItemFieldValue;
        }
    }
}