基于ASP.NET AJAX的WebPart开发与部署

; if (this.Controls.Contains(_ErrorContainer))
            {
                //this way of generating a unique control id is used in some of the OOB web parts
                int uniqueCounter;
                if (HttpContext.Current.Items["GetUniqueControlId"] != null)
                {
                    uniqueCounter = (int)HttpContext.Current.Items["GetUniqueControlId"];
                }
                else
                {
                    uniqueCounter = 0;
                }
                uniqueCounter++;
                HttpContext.Current.Items["GetUniqueControlId"] = uniqueCounter;

                //create a custom validator to register the current error message with the ValidationSummary control
                CustomValidator cv = new CustomValidator();
                cv.ID = string.Concat("_Error_", uniqueCounter);
                cv.ValidationGroup = _ValidationGroupId;
                cv.Display = ValidatorDisplay.None;
                cv.IsValid = false;
                cv.ErrorMessage = message;

                this.Controls.Add(cv);
            }
            else
            {
                //if RegisterError is called before the CreateChildCo