how to write update query for fileupload in asp.net

try
        {              
            connection.Open();
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = connection;
            cmd.CommandTimeout = 0;


           // cmd.CommandText = "UPDATE CREDOnet_Documents.dbo.SubUnitDocs  SET FileName= '" + sFilename + "',File=" + fileData + ",ContentType='" + contentType + "' WHERE ID =16";

            cmd.CommandText = "UPDATE CREDOnet_Documents.dbo.SubUnitDocs  SET @FileName,@FileBlob,@ContentType WHERE @LeaseDocID";


            cmd.Parameters.Add("@FileName", SqlDbType.NVarChar, 200);
            cmd.Parameters.Add("@File", SqlDbType.Image);
            cmd.Parameters.Add("@ContentType", SqlDbType.NVarChar, 200);
            cmd.Parameters.Add("@UpdatedBy", SqlDbType.NVarChar, 100);
            cmd.Parameters.Add("@UpdatedOn", SqlDbType.DateTime, 200);
            cmd.Parameters.Add("@ID", SqlDbType.Int);


            cmd.Parameters["@FileName"].Value = sFilename;
            cmd.Parameters["@File"].Value = fileData;
            cmd.Parameters["@ContentType"].Value = contentType;
            cmd.Parameters["@UpdatedBy"].Value = "System";
            cmd.Parameters["@UpdatedOn"].Value = System.DateTime.Now;
            cmd.Parameters["@ID"].Value = "16";


            cmd.CommandType = CommandType.Text;
            cmd.ExecuteNonQuery();
        }
        catch
        {

        }
        finally
        {
            connection.Close();
        }