本文介绍了对象不能从DBNull转换为其他类型的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
对象不能从DBNull转换为其他类型。
我有一个下面的函数会抛出上述错误。我在处理存储过程,并在C#code所有空值。
所以它从哪儿得到这个错误?
我可以看到在catch块中的错误。但我不理解这行下面创建()得到的错误。
公共布尔创建(DataTO DataTO)
{
IDbTrans交易= NULL;
IDbCmd IDbCmd;
字符串EncryptedPassword =加密(DataTO.txtPwd);
基地dataAccCom = NULL;
尝试
{
dataAccCom = Factory.Create();
dataAccCom.OpenConnection();
交易= dataAccCom.BeginTransaction();
IDbCmd = dataAccCom.CreateCommand(sp_Register,真正的);
dataAccCom.AddParameter(IDbCmdop_Id,DbType.Int64,0,ParameterDirection.Output);
dataAccCom.AddParameter(IDbCmdp_dlstTitle,DbType.String,ReplaceNull(DataTO.dlstTitle));
dataAccCom.AddParameter(IDbCmdp_txtFirstName,DbType.String,ReplaceNull(DataTO.txtFirstName));
dataAccCom.AddParameter(IDbCmdp_txtMiddleName,DbType.String,ReplaceNull(DataTO.txtMiddleName));
dataAccCom.AddParameter(IDbCmdp_txtLastName,DbType.String,ReplaceNull(DataTO.txtLastName));
dataAccCom.AddParameter(IDbCmd,p_txtDob,DbType.DateTime,DataTO.txtDob);
dataAccCom.AddParameter(IDbCmdp_txtDesig,DbType.String,ReplaceNull(DataTO.txtDesig));
dataAccCom.AddParameter(IDbCmdp_txtOFlatNo,DbType.String,ReplaceNull(DataTO.txtOFlatNo));
dataAccCom.AddParameter(IDbCmdp_txtOBuild,DbType.String,ReplaceNull(DataTO.txtOBuild));
dataAccCom.AddParameter(IDbCmdp_txtOPost,DbType.String,ReplaceNull(DataTO.txtOPost));
dataAccCom.AddParameter(IDbCmdp_txtOArea,DbType.String,ReplaceNull(DataTO.txtOArea));
dataAccCom.AddParameter(IDbCmdp_txtOCity,DbType.String,ReplaceNull(DataTO.txtOCity));
dataAccCom.AddParameter(IDbCmdp_txtRBuild,DbType.String,ReplaceNull(DataTO.txtRBuild));
dataAccCom.AddParameter(IDbCmdp_txtRPost,DbType.String,ReplaceNull(DataTO.txtRPost));
dataAccCom.AddParameter(IDbCmdp_txtUserID,DbType.String,ReplaceNull(DataTO.txtUserID));
dataAccCom.AddParameter(IDbCmdp_txtPwd,DbType.String,ReplaceNull(EncryptedPassword));
dataAccCom.ExecuteNonQuery(IDbCmd);
DataTO.Id = Convert.ToInt64(dataAccCom.GetParameterValue(IDbCmdop_Id));
器transaction.commit();
返回true;
}
赶上(System.Exception的前)
{
如果(交易!= NULL)
{
transaction.Rollback();
}
抛出前;
}
最后
{
交易= NULL;
如果(dataAccCom!= NULL)
{
dataAccCom.CloseConnection();
}
dataAccCom = NULL;
IDbCmd = NULL;
}
}
公共字符串ReplaceNull(字符串值)
{
如果(价值== NULL)
{
返回 ;
}
其他
{
返回值;
}
}
公开日期时间ReplaceNull(DateTime值)
{
如果(价值== NULL)
{
返回DateTime.Now;
}
其他
{
返回值;
}
}
公共双ReplaceNull(double值)
{
如果(价值== NULL)
{
返回0.0;
}
其他
{
返回值;
}
}
解决方案
我在想,你的输出参数是回来了为DBNull值。添加一个检查,像这样
VAR outputParam = dataAccCom.GetParameterValue(IDbCmd,op_Id);
如果(!(outputParam是为DBNull))
DataTO.Id = Convert.ToInt64(outputParam);
Object cannot be cast from DBNull to other types.
I have a following function which throws the above error. I am handling all nulls in store procedure and in the C# code.
So where is it getting this error?
I can see the error in the catch block. But i am not understanding which line in the following create() getting the error.
public Boolean Create(DataTO DataTO)
{
IDbTrans transaction = null;
IDbCmd IDbCmd;
string EncryptedPassword = Encrypt(DataTO.txtPwd);
Base dataAccCom = null;
try
{
dataAccCom = Factory.Create();
dataAccCom.OpenConnection();
transaction = dataAccCom.BeginTransaction();
IDbCmd = dataAccCom.CreateCommand("sp_Register", true);
dataAccCom.AddParameter(IDbCmd, "op_Id", DbType.Int64, 0, ParameterDirection.Output);
dataAccCom.AddParameter(IDbCmd, "p_dlstTitle", DbType.String, ReplaceNull(DataTO.dlstTitle));
dataAccCom.AddParameter(IDbCmd, "p_txtFirstName", DbType.String, ReplaceNull(DataTO.txtFirstName));
dataAccCom.AddParameter(IDbCmd, "p_txtMiddleName", DbType.String, ReplaceNull(DataTO.txtMiddleName));
dataAccCom.AddParameter(IDbCmd, "p_txtLastName", DbType.String, ReplaceNull(DataTO.txtLastName));
dataAccCom.AddParameter(IDbCmd, "p_txtDob", DbType.DateTime, DataTO.txtDob);
dataAccCom.AddParameter(IDbCmd, "p_txtDesig", DbType.String, ReplaceNull(DataTO.txtDesig));
dataAccCom.AddParameter(IDbCmd, "p_txtOFlatNo", DbType.String, ReplaceNull(DataTO.txtOFlatNo));
dataAccCom.AddParameter(IDbCmd, "p_txtOBuild", DbType.String, ReplaceNull(DataTO.txtOBuild));
dataAccCom.AddParameter(IDbCmd, "p_txtOPost", DbType.String, ReplaceNull(DataTO.txtOPost));
dataAccCom.AddParameter(IDbCmd, "p_txtOArea", DbType.String, ReplaceNull(DataTO.txtOArea));
dataAccCom.AddParameter(IDbCmd, "p_txtOCity", DbType.String, ReplaceNull(DataTO.txtOCity));
dataAccCom.AddParameter(IDbCmd, "p_txtRBuild", DbType.String, ReplaceNull(DataTO.txtRBuild));
dataAccCom.AddParameter(IDbCmd, "p_txtRPost", DbType.String, ReplaceNull(DataTO.txtRPost));
dataAccCom.AddParameter(IDbCmd, "p_txtUserID", DbType.String,ReplaceNull(DataTO.txtUserID));
dataAccCom.AddParameter(IDbCmd, "p_txtPwd", DbType.String, ReplaceNull(EncryptedPassword));
dataAccCom.ExecuteNonQuery(IDbCmd);
DataTO.Id = Convert.ToInt64(dataAccCom.GetParameterValue(IDbCmd, "op_Id"));
transaction.Commit();
return true;
}
catch (System.Exception ex)
{
if (transaction != null)
{
transaction.Rollback();
}
throw ex;
}
finally
{
transaction = null;
if (dataAccCom != null)
{
dataAccCom.CloseConnection();
}
dataAccCom = null;
IDbCmd = null;
}
}
public string ReplaceNull(string value)
{
if (value == null)
{
return "";
}
else
{
return value;
}
}
public DateTime ReplaceNull(DateTime value)
{
if (value == null)
{
return DateTime.Now;
}
else
{
return value;
}
}
public double ReplaceNull(double value)
{
if (value == null)
{
return 0.0;
}
else
{
return value;
}
}
解决方案
I'm thinking that your output parameter is coming back with a DBNull value. Add a check for that like this
var outputParam = dataAccCom.GetParameterValue(IDbCmd, "op_Id");
if(!(outputParam is DBNull))
DataTO.Id = Convert.ToInt64(outputParam);
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