Dapper QuerySingleOrDefault doesn't return null












1














Why Dapper QuerySingleOrDefault doesn't return null?
I use hard qwery.
In result I have object with default fields.
I ran this query in DB Browser for SQLite, It returned 0 rows.



public static Sensor GetSensor(string ip, string sensorName)
{
string sql = @"SELECT ip, name, invert, enable FROM DeviceAndOids AS A JOIN
DeviceForMonitoring AS B ON A.deviceForMonitoringKey=B.key JOIN
DeviceTypes AS C ON B.deviceTypeId=C.id WHERE
oidForDeviceKey IN (SELECT key FROM OidsForDevice WHERE
deviceTypeId IN (SELECT deviceTypeId FROM DeviceForMonitoring WHERE
ip = @ip) AND
name = @sensorName)";

using (IDbConnection cnn = new SQLiteConnection(LoadConnectionString()))
{
var result = cnn.QuerySingleOrDefault<Sensor>(sql, new { ip, sensorName });
return result;
}
}









share|improve this question






















  • As you can see in the documentation, if there's no item it will return the default (nothing), if there's one item it will return the item and if there's many items it will return a exception. So it's not returning null because it's not supposed to return null.
    – ikerbera
    Nov 20 at 8:47








  • 1




    @ikerbera, thanks, I was reading. Вut what is default in my case? I thought default for object is null
    – Дмитрий Суворов
    Nov 20 at 8:54










  • What is the value in result? You probably have a Sensor class variable with all it's properties at default value. ints at 0, strings at null, bools as false and so on.
    – ikerbera
    Nov 20 at 9:00












  • @ikerbera I would like use if (result != null) { // do something}
    – Дмитрий Суворов
    Nov 20 at 9:04










  • Can you show your Sensor class? I'm sure we can find some property that you can check to know if you got no data.
    – ikerbera
    Nov 20 at 9:09
















1














Why Dapper QuerySingleOrDefault doesn't return null?
I use hard qwery.
In result I have object with default fields.
I ran this query in DB Browser for SQLite, It returned 0 rows.



public static Sensor GetSensor(string ip, string sensorName)
{
string sql = @"SELECT ip, name, invert, enable FROM DeviceAndOids AS A JOIN
DeviceForMonitoring AS B ON A.deviceForMonitoringKey=B.key JOIN
DeviceTypes AS C ON B.deviceTypeId=C.id WHERE
oidForDeviceKey IN (SELECT key FROM OidsForDevice WHERE
deviceTypeId IN (SELECT deviceTypeId FROM DeviceForMonitoring WHERE
ip = @ip) AND
name = @sensorName)";

using (IDbConnection cnn = new SQLiteConnection(LoadConnectionString()))
{
var result = cnn.QuerySingleOrDefault<Sensor>(sql, new { ip, sensorName });
return result;
}
}









share|improve this question






















  • As you can see in the documentation, if there's no item it will return the default (nothing), if there's one item it will return the item and if there's many items it will return a exception. So it's not returning null because it's not supposed to return null.
    – ikerbera
    Nov 20 at 8:47








  • 1




    @ikerbera, thanks, I was reading. Вut what is default in my case? I thought default for object is null
    – Дмитрий Суворов
    Nov 20 at 8:54










  • What is the value in result? You probably have a Sensor class variable with all it's properties at default value. ints at 0, strings at null, bools as false and so on.
    – ikerbera
    Nov 20 at 9:00












  • @ikerbera I would like use if (result != null) { // do something}
    – Дмитрий Суворов
    Nov 20 at 9:04










  • Can you show your Sensor class? I'm sure we can find some property that you can check to know if you got no data.
    – ikerbera
    Nov 20 at 9:09














1












1








1







Why Dapper QuerySingleOrDefault doesn't return null?
I use hard qwery.
In result I have object with default fields.
I ran this query in DB Browser for SQLite, It returned 0 rows.



public static Sensor GetSensor(string ip, string sensorName)
{
string sql = @"SELECT ip, name, invert, enable FROM DeviceAndOids AS A JOIN
DeviceForMonitoring AS B ON A.deviceForMonitoringKey=B.key JOIN
DeviceTypes AS C ON B.deviceTypeId=C.id WHERE
oidForDeviceKey IN (SELECT key FROM OidsForDevice WHERE
deviceTypeId IN (SELECT deviceTypeId FROM DeviceForMonitoring WHERE
ip = @ip) AND
name = @sensorName)";

using (IDbConnection cnn = new SQLiteConnection(LoadConnectionString()))
{
var result = cnn.QuerySingleOrDefault<Sensor>(sql, new { ip, sensorName });
return result;
}
}









share|improve this question













Why Dapper QuerySingleOrDefault doesn't return null?
I use hard qwery.
In result I have object with default fields.
I ran this query in DB Browser for SQLite, It returned 0 rows.



public static Sensor GetSensor(string ip, string sensorName)
{
string sql = @"SELECT ip, name, invert, enable FROM DeviceAndOids AS A JOIN
DeviceForMonitoring AS B ON A.deviceForMonitoringKey=B.key JOIN
DeviceTypes AS C ON B.deviceTypeId=C.id WHERE
oidForDeviceKey IN (SELECT key FROM OidsForDevice WHERE
deviceTypeId IN (SELECT deviceTypeId FROM DeviceForMonitoring WHERE
ip = @ip) AND
name = @sensorName)";

using (IDbConnection cnn = new SQLiteConnection(LoadConnectionString()))
{
var result = cnn.QuerySingleOrDefault<Sensor>(sql, new { ip, sensorName });
return result;
}
}






c# dapper






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asked Nov 20 at 8:44









Дмитрий Суворов

195




195












  • As you can see in the documentation, if there's no item it will return the default (nothing), if there's one item it will return the item and if there's many items it will return a exception. So it's not returning null because it's not supposed to return null.
    – ikerbera
    Nov 20 at 8:47








  • 1




    @ikerbera, thanks, I was reading. Вut what is default in my case? I thought default for object is null
    – Дмитрий Суворов
    Nov 20 at 8:54










  • What is the value in result? You probably have a Sensor class variable with all it's properties at default value. ints at 0, strings at null, bools as false and so on.
    – ikerbera
    Nov 20 at 9:00












  • @ikerbera I would like use if (result != null) { // do something}
    – Дмитрий Суворов
    Nov 20 at 9:04










  • Can you show your Sensor class? I'm sure we can find some property that you can check to know if you got no data.
    – ikerbera
    Nov 20 at 9:09


















  • As you can see in the documentation, if there's no item it will return the default (nothing), if there's one item it will return the item and if there's many items it will return a exception. So it's not returning null because it's not supposed to return null.
    – ikerbera
    Nov 20 at 8:47








  • 1




    @ikerbera, thanks, I was reading. Вut what is default in my case? I thought default for object is null
    – Дмитрий Суворов
    Nov 20 at 8:54










  • What is the value in result? You probably have a Sensor class variable with all it's properties at default value. ints at 0, strings at null, bools as false and so on.
    – ikerbera
    Nov 20 at 9:00












  • @ikerbera I would like use if (result != null) { // do something}
    – Дмитрий Суворов
    Nov 20 at 9:04










  • Can you show your Sensor class? I'm sure we can find some property that you can check to know if you got no data.
    – ikerbera
    Nov 20 at 9:09
















As you can see in the documentation, if there's no item it will return the default (nothing), if there's one item it will return the item and if there's many items it will return a exception. So it's not returning null because it's not supposed to return null.
– ikerbera
Nov 20 at 8:47






As you can see in the documentation, if there's no item it will return the default (nothing), if there's one item it will return the item and if there's many items it will return a exception. So it's not returning null because it's not supposed to return null.
– ikerbera
Nov 20 at 8:47






1




1




@ikerbera, thanks, I was reading. Вut what is default in my case? I thought default for object is null
– Дмитрий Суворов
Nov 20 at 8:54




@ikerbera, thanks, I was reading. Вut what is default in my case? I thought default for object is null
– Дмитрий Суворов
Nov 20 at 8:54












What is the value in result? You probably have a Sensor class variable with all it's properties at default value. ints at 0, strings at null, bools as false and so on.
– ikerbera
Nov 20 at 9:00






What is the value in result? You probably have a Sensor class variable with all it's properties at default value. ints at 0, strings at null, bools as false and so on.
– ikerbera
Nov 20 at 9:00














@ikerbera I would like use if (result != null) { // do something}
– Дмитрий Суворов
Nov 20 at 9:04




@ikerbera I would like use if (result != null) { // do something}
– Дмитрий Суворов
Nov 20 at 9:04












Can you show your Sensor class? I'm sure we can find some property that you can check to know if you got no data.
– ikerbera
Nov 20 at 9:09




Can you show your Sensor class? I'm sure we can find some property that you can check to know if you got no data.
– ikerbera
Nov 20 at 9:09












1 Answer
1






active

oldest

votes


















1














Sensor was struct . I changed it to class
It works now






share|improve this answer





















  • Note: it might have worked (re null) if you had used <Sensor?> instead of <Sensor> - however, I strongly suspect that using struct for something that represents a data row is probably a bad idea that could cause multiple subtle confusions
    – Marc Gravell
    Nov 20 at 15:15










  • Maybe, I didn't understand you very well. But I changed it to class. I didn't use <Sensor?>
    – Дмитрий Суворов
    Nov 20 at 16:39










  • fair enough; changing it to class is by far the best solution here
    – Marc Gravell
    Nov 20 at 16:48











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1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes









1














Sensor was struct . I changed it to class
It works now






share|improve this answer





















  • Note: it might have worked (re null) if you had used <Sensor?> instead of <Sensor> - however, I strongly suspect that using struct for something that represents a data row is probably a bad idea that could cause multiple subtle confusions
    – Marc Gravell
    Nov 20 at 15:15










  • Maybe, I didn't understand you very well. But I changed it to class. I didn't use <Sensor?>
    – Дмитрий Суворов
    Nov 20 at 16:39










  • fair enough; changing it to class is by far the best solution here
    – Marc Gravell
    Nov 20 at 16:48
















1














Sensor was struct . I changed it to class
It works now






share|improve this answer





















  • Note: it might have worked (re null) if you had used <Sensor?> instead of <Sensor> - however, I strongly suspect that using struct for something that represents a data row is probably a bad idea that could cause multiple subtle confusions
    – Marc Gravell
    Nov 20 at 15:15










  • Maybe, I didn't understand you very well. But I changed it to class. I didn't use <Sensor?>
    – Дмитрий Суворов
    Nov 20 at 16:39










  • fair enough; changing it to class is by far the best solution here
    – Marc Gravell
    Nov 20 at 16:48














1












1








1






Sensor was struct . I changed it to class
It works now






share|improve this answer












Sensor was struct . I changed it to class
It works now







share|improve this answer












share|improve this answer



share|improve this answer










answered Nov 20 at 9:45









Дмитрий Суворов

195




195












  • Note: it might have worked (re null) if you had used <Sensor?> instead of <Sensor> - however, I strongly suspect that using struct for something that represents a data row is probably a bad idea that could cause multiple subtle confusions
    – Marc Gravell
    Nov 20 at 15:15










  • Maybe, I didn't understand you very well. But I changed it to class. I didn't use <Sensor?>
    – Дмитрий Суворов
    Nov 20 at 16:39










  • fair enough; changing it to class is by far the best solution here
    – Marc Gravell
    Nov 20 at 16:48


















  • Note: it might have worked (re null) if you had used <Sensor?> instead of <Sensor> - however, I strongly suspect that using struct for something that represents a data row is probably a bad idea that could cause multiple subtle confusions
    – Marc Gravell
    Nov 20 at 15:15










  • Maybe, I didn't understand you very well. But I changed it to class. I didn't use <Sensor?>
    – Дмитрий Суворов
    Nov 20 at 16:39










  • fair enough; changing it to class is by far the best solution here
    – Marc Gravell
    Nov 20 at 16:48
















Note: it might have worked (re null) if you had used <Sensor?> instead of <Sensor> - however, I strongly suspect that using struct for something that represents a data row is probably a bad idea that could cause multiple subtle confusions
– Marc Gravell
Nov 20 at 15:15




Note: it might have worked (re null) if you had used <Sensor?> instead of <Sensor> - however, I strongly suspect that using struct for something that represents a data row is probably a bad idea that could cause multiple subtle confusions
– Marc Gravell
Nov 20 at 15:15












Maybe, I didn't understand you very well. But I changed it to class. I didn't use <Sensor?>
– Дмитрий Суворов
Nov 20 at 16:39




Maybe, I didn't understand you very well. But I changed it to class. I didn't use <Sensor?>
– Дмитрий Суворов
Nov 20 at 16:39












fair enough; changing it to class is by far the best solution here
– Marc Gravell
Nov 20 at 16:48




fair enough; changing it to class is by far the best solution here
– Marc Gravell
Nov 20 at 16:48


















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