ASP.NET

HtmlForm form = new HtmlForm();
string attachment = "attachment; filename=Employee.xls";
Response.ClearContent();
Response.AddHeader("content-disposition", attachment);
Response.ContentType = "application/ms-excel";
StringWriter stw = new StringWriter();
HtmlTextWriter htextw = new HtmlTextWriter(stw);
form.Controls.Add(gvEmployee);
this.Controls.Add(form);
form.RenderControl(htextw);
Response.Write(stw.ToString());
Response.End();

if (!this.CheckObjectivesCheckBoxesValid())
{
    var repeaterValidator = new CustomValidator();
    repeaterValidator.IsValid = false;
    repeaterValidator.ErrorMessage = "Please select at least one objective.";
    Page.Validators.Add(repeaterValidator);
}

if (string.IsNullOrEmpty(this.txtDetails.Text) && string.IsNullOrEmpty(this.txtSuggestions.Text) && string.IsNullOrEmpty(this.txtSupportingEvidence.Text))
{
    var requiredFields = new CustomValidator();
    requiredFields.IsValid = false;
    requiredFields.ErrorMessage = "You must include information in at least one of Details, Suggestions or Evidence";
    Page.Validators.Add(requiredFields);
}