报错：
“System.InvalidCastException”类型的异常在 System.Data.dll 中发生，但未在用户代码中进行处理 其他信息: 指定的转换无效。
解决方法：
修改前的代码示例
public AccessoryInfo GetInfo(Int32 accessoryId){AccessoryInfo entity = null;SqlParameter[] parms = new SqlParameter[]{new SqlParameter("@FieldValue", SqlDbType.NVarChar, 50),new SqlParameter("@IsByID", SqlDbType.Bit)};parms[0].Value = accessoryId;parms[1].Value = true;using (SqlDataReader rdr = SQLHelper.ExecuteReaderStoredProcedure(SQLHelper.MESConnString, "Prod_Accessory_GetInfo", parms)){if (rdr.Read()){//entity = new AccessoryInfo(rdr.GetInt32(0), rdr.GetString(1), rdr.GetString(2), rdr.GetString(3), rdr.GetString(4),// rdr.GetInt32(5), rdr.GetDouble(6), rdr.GetDateTime(7), rdr.GetString(8), rdr.GetDecimal(9),// rdr.GetDecimal(10), rdr.GetDateTime(11), rdr.GetString(12), rdr.GetDateTime(13), rdr.GetDateTime(14), rdr.GetString(15), rdr.GetDateTime(20), rdr.GetDateTime(21), rdr.GetDateTime(22));entity = new AccessoryInfo();entity.AccessoryId = rdr.GetInt32(0);entity.AccessoryCodoe = rdr.GetString(1);entity.AccessoryName = rdr.GetString(2);entity.Lot = rdr.GetString(3);entity.SerialNumber = rdr.GetString(4);entity.Status = rdr.GetInt32(5);entity.UserTime = rdr.GetFloat(6);entity.LoseTime = rdr.GetDateTime(7);entity.SupplierCode = rdr.GetString(8);entity.InStockQty = rdr.GetDecimal(9);entity.CurrentQty = rdr.GetDecimal(10);entity.StartThawTime = rdr.GetDateTime(11);entity.CreateBy = rdr.GetString(12);entity.CreateTime = rdr.GetDateTime(13);entity.UnsealTime = rdr.GetDateTime(14);entity.AccessoryTypeName = rdr.GetString(15);entity.SupplierName = rdr.GetString(16);entity.AccessoryType = rdr.GetInt32(17);entity.ProdDateTime = rdr.GetDateTime(18);entity.ItemId = rdr.GetInt32(19);entity.EndThawTime = rdr.GetDateTime(20);entity.EndStirTime = rdr.GetDateTime(21);entity.KaifengTime= rdr.GetDateTime(22);}rdr.Close();}return entity;}
修改后的代码示例
public AccessoryInfo GetInfo(Int32 accessoryId)
{AccessoryInfo entity = null;SqlParameter[] parms = new SqlParameter[]{new SqlParameter("@FieldValue", SqlDbType.NVarChar, 50),new SqlParameter("@IsByID", SqlDbType.Bit)};parms[0].Value = accessoryId;parms[1].Value = true;using (SqlDataReader rdr = SQLHelper.ExecuteReaderStoredProcedure(SQLHelper.MESConnString, "Prod_Accessory_GetInfo", parms)){if (rdr.Read()){entity = new AccessoryInfo();entity.AccessoryId = rdr.GetInt32(rdr.GetOrdinal("AccessoryId"));entity.AccessoryCodoe = Convert.ToString(rdr["AccessoryCodoe"]);entity.AccessoryName = Convert.ToString(rdr["AccessoryName"]);entity.Lot = Convert.ToString(rdr["Lot"]);entity.SerialNumber = Convert.ToString(rdr["SerialNumber"]);entity.Status = Convert.ToInt32(rdr["Status"]);entity.UserTime = Convert.ToDouble(rdr["UserTime"]);entity.LoseTime = Convert.ToDateTime(rdr["LoseTime"]);entity.SupplierCode = Convert.ToString(rdr["SupplierCode"]);entity.InStockQty = Convert.ToDecimal(rdr["InStockQty"]);entity.CurrentQty = Convert.ToDecimal(rdr["CurrentQty"]);entity.StartThawTime = Convert.ToDateTime(rdr["StartThawTime"]);entity.CreateBy = Convert.ToString(rdr["CreateBy"]);entity.CreateTime = Convert.ToDateTime(rdr["CreateTime"]);entity.UnsealTime = Convert.ToDateTime(rdr["UnsealTime"]);entity.AccessoryTypeName = Convert.ToString(rdr["AccessoryTypeName"]);entity.SupplierName = Convert.ToString(rdr["SupplierName"]);entity.AccessoryType = Convert.ToInt32(rdr["AccessoryType"]);entity.ProdDateTime = Convert.ToDateTime(rdr["ProdDateTime"]);entity.ItemId = Convert.ToInt32(rdr["ItemID"]);entity.EndThawTime = Convert.ToDateTime(rdr["EndThawTime"]);entity.EndStirTime = Convert.ToDateTime(rdr["EndStirTime"]);entity.KaifengTime = Convert.ToDateTime(rdr["KaifengTime"]);}rdr.Close();}return entity;
}
之后报错：
entity.EndThawTime = Convert.ToDateTime(rdr["EndThawTime"]); entity.EndStirTime = Convert.ToDateTime(rdr["EndStirTime"]); entity.KaifengTime = Convert.ToDateTime(rdr["KaifengTime"]);
报错： “System.InvalidCastException”类型的异常在 mscorlib.dll 中发生，但未在用户代码中进行处理 其他信息: 对象不能从 DBNull 转换为其他类型。
处理方法：
修改后的 SQL 查询
SELECT [AccessoryId], [AccessoryCodoe], [AccessoryName], [Lot], [SerialNumber], t.[Status], [UserTime], ISNULL([LoseTime], '1900-01-01') AS [LoseTime], [SupplierCode], [InStockQty], [CurrentQty], ISNULL([StartThawTime], '1900-01-01') AS [StartThawTime], t.[CreateBy], t.[CreateTime], ISNULL([UnsealTime], '1900-01-01') AS [UnsealTime], t1.AccessoryTypeName,t2.VendorName AS SupplierName,t.AccessoryType,t.ProdDateTime,bi.ItemID,ISNULL(t.EndThawTime, '1900-01-01') AS EndThawTime,ISNULL(t.EndStirTime, '1900-01-01') AS EndStirTime,ISNULL(t.KaifengTime, '1900-01-01') AS KaifengTime FROM [Prod_Accessory] t JOIN dbo.Prod_AccessoryType t1 ON t1.AccessoryTypeId = t.AccessoryType JOIN dbo.Basal_Supplier t2 ON t2.VendorCode = t.SupplierCode JOIN dbo.Basal_Item AS bi ON t.AccessoryCodoe = bi.ItemCode WHERE [AccessoryId] = 52;
