ASP.Net FileUpload: Rename file name before saving if already exists

This way

HTML

<asp:FileUpload ID="FileUpload1" runat="server" />
&nbsp;
<asp:Button ID="btnUpload" Text="Upload" runat="server" OnClick="FileUpload" />

Namespace

using System.IO;

C#

protected void FileUpload(object sender, EventArgs e)
{

    int count = 0;
    string filename = string.Empty;
    if (this.FileUpload1.HasFile)
    {
        string ext = Path.GetExtension(FileUpload1.PostedFile.FileName);
        string[] files = Directory.GetFiles(Server.MapPath("~/Files/"));
        if (File.Exists(Server.MapPath("~/Files/") + Path.GetFileName(FileUpload1.PostedFile.FileName)))
        {
            foreach (string s in files)
            {

                filename = Path.GetFileName(s).Substring(0, Path.GetFileName(s).LastIndexOf("."));
                if (filename.Contains("("))
                {
                    filename = filename.Substring(0, filename.LastIndexOf("("));
                }

                if (filename == Path.GetFileName(FileUpload1.PostedFile.FileName).Substring(0, Path.GetFileName(FileUpload1.PostedFile.FileName).LastIndexOf(".")))
                {
                    count++;
                }
            }
            this.FileUpload1.PostedFile.SaveAs(Server.MapPath("~/Files/") + filename + "(" + count.ToString() + ")" + ext);
        }

        else
        {
            this.FileUpload1.PostedFile.SaveAs(Server.MapPath("~/Files/") + Path.GetFileName(FileUpload1.PostedFile.FileName));
        }
    }
}

 Using TextBox to change Uploaded file name

 HTML

<form id="form1" runat="server">
<div>
    File name =
    <asp:TextBox ID="txtFileName" Text="SaharaDesert" runat="server" />
    <br />
    <asp:FileUpload ID="FileUpload1" runat="server" />
    &nbsp;
    <asp:Button ID="btnUpload" Text="Upload" runat="server" OnClick="FileUpload" />
</div>
</form>

C#

protected void FileUpload(object sender, EventArgs e)
{
 
    int count = 0;
    if (this.FileUpload1.HasFile && !string.IsNullOrEmpty(this.txtFileName.Text))
    {
        string ext = Path.GetExtension(FileUpload1.PostedFile.FileName);
        string[] files = Directory.GetFiles(Server.MapPath("~/Files/"));
        if (File.Exists(Server.MapPath("~/Files/") + this.txtFileName.Text + ext))
        {
            foreach (string s in files)
            {
                string filename = string.Empty;
                filename = Path.GetFileName(s).Substring(0, Path.GetFileName(s).LastIndexOf("."));
                if (filename.Contains("("))
                {
                    filename = filename.Substring(0, filename.LastIndexOf("("));
                }
 
                if (filename == this.txtFileName.Text.Trim())
                {
                    count++;
                }
            }
            this.FileUpload1.PostedFile.SaveAs(Server.MapPath("~/Files/") + this.txtFileName.Text + "(" + count.ToString() + ")" + ext);
        }
 
        else
        {
            this.FileUpload1.PostedFile.SaveAs(Server.MapPath("~/Files/") + this.txtFileName.Text + ext);
        }
    }
}