How to save the Export to Excel file from Gridview to Specific Folder in C#

SqlConnection con = new SqlConnection();

con.Open();

SqlCommand cmd = new SqlCommand();

cmd.Connection = con;

cmd.CommandType = CommandType.StoredProcedure;

cmd.CommandText = "SP_GelAllEmaployeeDetail";

SqlDataAdapter da = new SqlDataAdapter(cmd);

DataSet ds = new DataSet();

da.Fill(ds);

gdvReport1A.DataSource = ds;

gdvReport1A.DataBind(); 

In Web.conf file i have folder name. Please find the settings of Web.Config file.

<add key="FolderName" value="TestFolder" />

 strFolderName = System.Configuration.ConfigurationManager.AppSettings["FolderName"].ToString();

 strFolderPath = strDirectoryPath + @"\" + strFolderName;

 DirectoryInfo dr = new DirectoryInfo(strFolderPath);

 if (dr.Exists == false)
 {
      dr.Create();
 }

 System.IO.StringWriter stringWrite = new System.IO.StringWriter();

 System.Web.UI.HtmlTextWriter htmlWrite = new HtmlTextWriter(stringWrite);

 gdvReport1A.RenderControl(htmlWrite);

 String renderedGridView = stringWrite.ToString();

 File.WriteAllText(@"C:\Royalty\Report1A.xls", renderedGridView);