select from list using LINQ's Where [closed]
select from list using LINQ's Where [closed]
I need to get the vehicle type according to vehicle number. I need to select specific column from a list according to another column.
Here is my code:
protected void ddVehicleNo_SelectedIndexChanged(object sender, EventArgs e)
List<Exp_VehicleDTO> odata = (List<Exp_VehicleDTO>)Session["VehicleDTO"];
var vehityeps=odata.Select(x=>x.VehicleNo.Contains(x.VehicleType.Equals(Convert.ToInt32(ddVehicleNo.SelectedValue))))
This code causes error "the best overload method match for "string.contains(string)" has some invalid arguments".
Exp_vehicleDTO class
public class Exp_VehicleDTO
public int CompanyId get; set;
public int VehicleId get; set;
public int VehicleType get; set;
public string VehicleNo get; set;
public int Status get; set;
public DateTime CreatedDateTime get; set;
public string CreatedBy get; set;
public string CreatedMachine get; set;
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x.VehicleType.Equals returns a boolean, you're now trying to find a boolean value in a string (VehicleNo). When you see that kind of error message, examine the method you're using and the information you're putting into it carefully.– John
Sep 12 '18 at 6:49
x.VehicleType.Equals
Equals returns a bool yet Contains expects a string.– Enigmativity
Sep 12 '18 at 6:51
Equals
bool
Contains
string
Yeah the bigmistake of this question was not giving your data types, and exactly what you wanted to return. though i was amused for 5 mintues.. job done
– Michael Randall
Sep 12 '18 at 6:58
"i did a mistake by converting to int32. " that is not the main mistake. If you want to filter you should use
Where and not Select, otherwise you get a collection of bool values. and Contains needs a string as input– Mong Zhu
Sep 12 '18 at 6:58
Where
Select
bool
Contains
string
2 Answers
2
You can get the vehicle type like so:
int vehicleType = odata.Single(x => x.VehicleNo.Equals(ddVehicleNo.SelectedValue)).VehicleType;
Single will take the first item that matches the condition. Note that it will throw an exception if the item isn't found, or if there are multiple matching items.
Single
If you want to handle the case that the item isn't found, you can do something like this:
var vehicle = odata.SingleOrDefault(x => x.VehicleNo.Equals(ddVehicleNo.SelectedValue));
if (vehicle != null)
var vehicleType = vehicle.VehicleType;
else
// set combobox's SelectedIndex to -1
how can i modify this to avoid exeption if the item isn't found?
– Didu
Sep 12 '18 at 7:22
@Didu updated :-) You can also swap
Single/SingleOrDefault for First/FirstOrDefault if you expect multiple items might have the same VehicleNo and you just want the first one.– John
Sep 12 '18 at 7:23
Single
SingleOrDefault
First
FirstOrDefault
VehicleNo
Works fine. thank you very much :)
– Didu
Sep 12 '18 at 7:25
It was a long road, but someone got there in the end, up vote
– Michael Randall
Sep 12 '18 at 7:31
Difficult to help without knowing what error you are receiving but try changing your code to this:
protected void ddVehicleNo_SelectedIndexChanged(object sender, EventArgs e)
List<Exp_VehicleDTO> odata = (List<Exp_VehicleDTO>)Session["VehicleDTO"];
var vehityeps = odata
.Where(v => v.VehicleNo.ToString() == ddVehicleNo.SelectedValue)
.Select(v => v.VehicleType);
That should populate vehityeps with all VehicleType's where VehicleNo equals what the user has selected in the ddVehicleNo drop down.
vehityeps
VehicleType
VehicleNo
ddVehicleNo
UPDATED
I'm not sure what types are used Exp_VehicleDTO but my guess is VehicleNo is an int. To be safe with my solution this compares the values as strings.
Exp_VehicleDTO
VehicleNo
int
but this gives a type conversion error
– Didu
Sep 12 '18 at 7:04
@Didu remove
int.Parse( ) around ddVehicleNo.SelectedValue - Jesse has assumed it's int since you didn't post your class definition on this question.– John
Sep 12 '18 at 7:05
int.Parse( )
ddVehicleNo.SelectedValue
done. but it recieves cannot implicity convert type string to bool
– Didu
Sep 12 '18 at 7:08
@John thanks for clarifying to @Didu the assumption of an
int. The assumption is based on Convert.ToInt32(ddVehicleNo.SelectedValue) from the code within the question.– Jesse Johnson
Sep 12 '18 at 7:11
int
Convert.ToInt32(ddVehicleNo.SelectedValue)
I would have made the same assumption :-)
– John
Sep 12 '18 at 7:13
What error are you getting, add information to the question
– Div
Sep 12 '18 at 6:45