调整excel字段解析方法，优化解析速度

Bailun.DC.Web/Base/NpolHelper.cs

@@ -191,21 +191,15 @@ namespace Bailun.DC.Web.Base
                 return string.Empty;
             switch (cell.CellType)
             {
+                case CellType.String:
+                    return cell.StringCellValue;
                 case CellType.Blank:
                     return string.Empty;
-                case CellType.Boolean:
-                    return cell.BooleanCellValue.ToString();
-                case CellType.Error:
-                    return cell.ErrorCellValue.ToString();
                 case CellType.Numeric:
                     short format = cell.CellStyle.DataFormat;
                     if (format == 14 || format == 31 || format == 57 || format == 58 || HSSFDateUtil.IsCellDateFormatted(cell)) return cell.DateCellValue.ToString("yyyy-MM-dd HH:mm:ss");
                     return cell.NumericCellValue.ToString();
-                case CellType.Unknown:
-                default:
-                    return cell.ToString();
-                case CellType.String:
-                    return cell.StringCellValue;
+                
                 case CellType.Formula:
                     try
                     {
@@ -215,8 +209,23 @@ namespace Bailun.DC.Web.Base
                     }
                     catch
                     {
-                        return cell.NumericCellValue.ToString();
+                        try
+                        {
+                            return cell.NumericCellValue.ToString();
+                        }
+                        catch (Exception ex)
+                        {
+                            return "0";
+                        }
+                        
                     }
+                case CellType.Boolean:
+                    return cell.BooleanCellValue.ToString();
+                case CellType.Error:
+                    return cell.ErrorCellValue.ToString();
+                case CellType.Unknown:
+                default:
+                    return cell.ToString();
             }
         }