Detectings Files before extract using Iconic zip

I am using Iconic.zip as a way of extracting files on a server but its for a theme pack. And I want to be able to check if a file exists in the zip file before unziping is this possible with the libary.

I am using the following code which works to upload and extract the files.

      if (fileUploadZipFiles.HasFile)
        {
            string uploadedZipFile = Path.GetFileName(fileUploadZipFiles.PostedFile.FileName);
            string zipFileLocation = Server.MapPath("~/Themes/" + uploadedZipFile);
            fileUploadZipFiles.SaveAs(zipFileLocation);

            ZipFile zipFileToExtract = ZipFile.Read(zipFileLocation);
            zipFileToExtract.ExtractAll(Server.MapPath("~/Themes/" + txtFolderName.Text.ToString()), ExtractExistingFileAction.DoNotOverwrite);
            gridviewExtractedFiles.DataSource = zipFileToExtract.Entries;
            gridviewExtractedFiles.DataBind();
            lblMessage.Text = "Zip file extracted successfully and containes following files";
        }

The second part of this question is that I am using master pages for my themes how would i go about setting the active theme to the one the user wants to make acitve. I am sure I have to have my own base page.

I found the anser to my first part of question was to use the following.

  if (fileUploadZipFiles.HasFile)
        {
            string uploadedZipFile = Path.GetFileName(fileUploadZipFiles.PostedFile.FileName);
            string zipFileLocation = Server.MapPath("~/Themes/" + uploadedZipFile);
            fileUploadZipFiles.SaveAs(zipFileLocation);

            ZipFile zipFileToExtract = ZipFile.Read(zipFileLocation);
                var result = zipFileToExtract.Any(entry => entry.FileName.EndsWith("site.master"));
                if (result == true)
                {

                    zipFileToExtract.ExtractAll(Server.MapPath("~/Themes/" + txtFolderName.Text.ToString()), ExtractExistingFileAction.DoNotOverwrite);
                    gridviewExtractedFiles.DataSource = zipFileToExtract.Entries;
                    gridviewExtractedFiles.DataBind();
                    lblMessage.Text = "Zip file extracted successfully and containes following files";
                }
                else 
                    lblMessage.Text = "Not a vlaid theme file.";

        }

As suggested here is the answer i used linq to check the existence of the file.

  protected void btnExtractZipFiles_Click(object sender, EventArgs e)
    {
        if (txtFolderName.Text == "")
        {
            lblMessage.Text = "A Folder Name must be specified";
        }else

        if (fileUploadZipFiles.HasFile)
        {

            string uploadedZipFile = Path.GetFileName(fileUploadZipFiles.PostedFile.FileName);
            string zipFileLocation = Server.MapPath("~/Themes/" + uploadedZipFile);
            fileUploadZipFiles.SaveAs(zipFileLocation);

            ZipFile zipFileToExtract = ZipFile.Read(zipFileLocation);
            var result = zipFileToExtract.Any(entry => entry.FileName.EndsWith("default.Master"));
                if (result == true)
                {

                    zipFileToExtract.ExtractAll(Server.MapPath("~/Themes/" + txtFolderName.Text.ToString()), ExtractExistingFileAction.DoNotOverwrite);
                    gridviewExtractedFiles.DataSource = zipFileToExtract.Entries;
                    gridviewExtractedFiles.DataBind();
                    lblMessage.Text = "Zip file extracted successfully and containes following files";
                    SetConfiguration(); //parse the configuration file
                }
                else 
                    lblMessage.Text = "Not a vlaid theme file.";

        }

    }