How do I copy /move all files from one folder in a web application to another web application in asp .net

In My point of view, you can't: The default permissions for the user your website is running under will almost certainly not allow you to access files in the root directory of your server, and your website cannot specify the storage location of a file on the client (or even if it is stored at all - that is up to the user)

For this we have indirect way the below code is retrieve file from DB Modify the Code based on your requirement

<![CDATA[<%  
    // Send a download file to the client given the filename.    
    string guid = Request.QueryString["file"];
    string fileName = "ERROR";
    byte[] data = new byte[] { 0, 0, 0, 0 };
    string strCon = System.Web.Configuration.WebConfigurationManager.ConnectionStrings["DownloadDatabase"].ConnectionString;
    using (System.Data.SqlClient.SqlConnection con = new System.Data.SqlClient.SqlConnection(strCon))
        {
        con.Open();
        string strcmd = "SELECT [iD] ,cn.[fileName],[description] ,[dataContent] ,[version] " +
                        "FROM dlContent cn " +
                        "WHERE cn.iD=@ID";
        using (System.Data.SqlClient.SqlCommand cmd = new System.Data.SqlClient.SqlCommand(strcmd, con))
            {
            cmd.Parameters.AddWithValue("@ID", guid);
            using (System.Data.SqlClient.SqlDataReader r = cmd.ExecuteReader())
                {
                if (r.Read())
                    {
                    fileName = (string) r["filename"];
                    data = (byte[]) r["dataContent"];
                    }
                }
            }
        }
    Response.Clear();
    Response.AddHeader("Cache-Control", "no-cache, must-revalidate, post-check=0, pre-check=0");
    Response.AddHeader("Pragma", "no-cache");
    Response.AddHeader("Content-Description", "File Download");
    Response.AddHeader("Content-Type", "application/force-download");
    Response.AddHeader("Content-Transfer-Encoding", "binary\n");
    Response.AddHeader("content-disposition", "attachment;filename=" + fileName);
    Response.BinaryWrite(data);
    Response.End();  
%>]]>

Save another applications directory path in your current applications config file and then using file.copy copy all the files from source to destination. if u want to move them them delete from current application after copying....

Use FTP, remember that a website could be hosted in a number of different ways, so you really don't want to get into specific about addresses, but connections can more easily be configuration items, which ultimately you can have different configurations for different environments (as could a path ... but ... just don't ;) )

Look at similar question here, Solution 3 will give you the code, it's pretty simple once you have the ftp server bit set up for the site.

How do I copy files from one web application to another in asp .net[^]

If both are in Same server it is easy.. if not.. create a WCF Service To Do your task