My project uses LINQ to SQL and EF to handle objects in the database. I have a status column in an entity object that is designated as an int. My BI layer updates this data with the below code, when i change the data, if i query SQL i see the updated value in the DB, however the UI layer is not displaying the new value, it shows the old one. Stopping the project in VS and re-starting it, then it will display the updated data.
Does EF do any caching? Could this be caused by having 3 seperate projects for Data, UI and BI?
Public Shared Function UpdateStatus(PersonID As Guid, Status As LeadStatus, UserName As String) As Boolean
Dim db As New MyDb.DBContainer
Dim z = (From p In db.People Where p.Id = PersonID).FirstOrDefault()
If Not IsNothing(z) Then
z.Status = Status
db.SaveChanges()
LeadLogFunctions.AddLog(LeadLogTypes.StatusChanged, PersonID, UserName, "Status Changed By: " & UserName & " To: " & Enumeration.GetEnumDescription(Status))
Return True
End If
Return False
End Function
The UI layer won't display the new value until you reload it from the database.
If you are keeping the same DbContext open, you should reload the existing entity rather than making a new query using the DbContext.Entry(of T)().Reload() function.
Related
I have tried to implement login page in ASP.NET Core MVC and using postgresql as database.
It should check whether user exits in the database table of postgresql and verify, so what is the query to search for user in database and made them sign in?
I have written my code like this:
public IActionResult Login(string seller_email, string seller_password)
{
using var connection = new NpgsqlConnection(connString);
connection.Open();
string main_query = String.Format(#"select exists(select 1 from public.""sellers"" where ""seller_email""='{0}')", seller_email);
using var command_main = new NpgsqlCommand(main_query, connection);
int result_main = command_main.ExecuteNonQuery();
if (result_main < 0)
{
return View(nameof(Create));
}
else
{
return View(nameof(Sign));
}
}
There is a seller table in the database, so just have to check seller exists or not - if exists the have to create a view for it
You are doing a select query, so you must use a command.ExecuteReader.
The ExecuteNonQuery is to be used with statements that update/insert/delete records.
BUT, most importantly, don't concatenate user submitted values into the query string, as it opens the door to SQL injections. Instead, used a parameter.
See the getting started doc for a simple example.
I have created a simple stored procedure in SQL Server 2008 as:
CREATE PROCEDURE viewPosts
AS
SELECT * FROM dbo.Post
Now, I have no idea how to use it in controller's action, I have a database object which is:
entities db = new entities();
Kindly tell me how to use stored procedure with this database object in Entity Framework.
For Details check this link:
http://www.entityframeworktutorial.net/data-read-using-stored-procedure.aspx
Hope this will help you.
See article about 30% in:
In the designer, right click on the entity and select Stored Procedure mapping.
Click and then click the drop down arrow that appears. This exposes the list of all Functions found in the DB metadata.
Select Procedure from the list. The designer will do its best job of matching the stored procedure’s parameters with the entity properties using the names. In this case, since all of the property names match the parameter names, it maps every one correctly so you don’t need to make any changes. Note: The designer is not able to automatically detect the name of the field being returned.
Under the Result Column Bindings section, click and enter variable name. The designer should automatically select the entity key property for this final mapping.
The following code is what I use to initialize the stored procedure, then obtain the result into variable returnedResult, which in this case is the record id of a newly created record.
SqlParameter paramResult = new SqlParameter("#Result", -1);
paramResult.Direction = System.Data.ParameterDirection.Output;
var addParameters = new List<SqlParameter>
{
new SqlParameter("#JobID", EvalModel.JobID),
new SqlParameter("#SafetyEvaluator", EvalModel.SafetyEvaluator),
new SqlParameter("#EvaluationGuid", EvalModel.EvaluationGuid),
new SqlParameter("#EvalType", EvalModel.EvalType),
new SqlParameter("#Completion", EvalModel.Completion),
new SqlParameter("#ManPower", EvalModel.ManPower),
new SqlParameter("#EDate", EvalModel.EDate),
new SqlParameter("#CreateDate", EvalModel.CreateDate),
new SqlParameter("#Deficiency", EvalModel.Deficiency.HasValue ? EvalModel.Deficiency.Value : 0),
new SqlParameter("#DeficiencyComment", EvalModel.DeficiencyComment != null ? EvalModel.DeficiencyComment : ""),
new SqlParameter("#Traffic", EvalModel.Traffic.HasValue ? EvalModel.Traffic.Value : 0),
paramResult
};
// Stored procedure name is AddEval
context.Database.ExecuteSqlCommand("AddEval #JobID, #SafetyEvaluator, #EvaluationGuid, #EvalType, #Completion, #ManPower, #EDate, #CreateDate, #Deficiency, #DeficiencyComment, #Traffic, #Result OUTPUT", addParameters.ToArray());
var returnedResult = paramResult.Value;
NewEvaluationID = Convert.ToInt32(returnedResult);
I have an ASP.NET page that needs to push a little data to an MS Access 2003 database. The process requires a Select on one record, Inserting one new record and Updating one record. I am connecting to the Access database via an OleDbConnection connection. So far, the Select and Insert functions are working exactly as expected (so I know my connection is good). The Update, however, fails to update any rows. The function to update the record looks like this:
public static int UpdateDeviceDates(int deviceId, DateTime nextTestDate)
{
var conn = DbConnect.AccessConnection();
var sqlString = WebConfigurationManager.AppSettings["UpdateDeviceDates"];
using (var cmd = new OleDbCommand(sqlString, conn))
{
cmd.Parameters.AddWithValue("#DeviceID", deviceId);
cmd.Parameters.AddWithValue("#NextTestDate", nextTestDate);
cmd.CommandType = CommandType.Text;
conn.Open();
var result = cmd.ExecuteNonQuery();
return result;
}
}
The sqlString pulled back from the web.config file looks like this:
UPDATE tblDevice
SET tblDevice.NextTestDate = #nextTestDate,
tblDevice.FirstNoticeDate = Null,
tblDevice.SecondNoticeDate = Null
WHERE DeviceID=#deviceId;
This query works fine if you paste it into a new Access query window and hit run, so I know the syntax is correct. I have done quite a bit of testing and figured out that it is the #nextTestDate field that is causing it to fail. When I took that out of the SQL string, it updated the record as expected. This is disconcerting, because the date I pass through to the Insert function works just fine.
I have looked around quite a bit and the closest I found to an answer was "Can't update date in aspx to a MS-ACCESS table". The main answer there was to change the parameter to a ShortDateString. I tried that to no effect. It was also suggested to bracket the date in #, since that is what Access does in its own queries. Unfortunately, that didn't work either.
I don't know why either of these should have been necessary, because the date comes through in exactly the same format as in the Insert statement and that works fine. I'm at my wits end here because the only thing I've found to make that query work is to remove the date parameter (which would defeat the main purpose of the query).
In your query, the parameters are in a different order, the order must match:
cmd.Parameters.AddWithValue("#NextTestDate", nextTestDate);
cmd.Parameters.AddWithValue("#DeviceID", deviceId);
To match:
UPDATE tblDevice
SET tblDevice.NextTestDate = #nextTestDate, <--- Param 1
tblDevice.FirstNoticeDate = Null,
tblDevice.SecondNoticeDate = Null
WHERE DeviceID=#deviceId; <--- Param 2
I have changed all my code from the raw ADO.NET SQLCommand to Entity Framework in order to have easier accessibility of changing my code in the future. However, I have realized there are many drawbacks in Entity Framework it is not as simple as injecting raw SQL commands into the database. Moreover, I have used Reverse Engineering to generate the Models & Mapping for MS Sql Server.
Currently, I am trying to do the following but none of the columns are getting updated.
string sql = #"UPDATE [ProductDB] SET CreatedProduct_Time=getdate(), CreatedProduct_Date=getdate()" + " WHERE [Material_No] = #Material_No";
db.Database.ExecuteSqlCommand(sql, new SqlParameter("#Material_No", materialnotxt));
The columns are not getting updated.
I am having a doubt whether Entity Framework will help me maintain my code for future use and is it worth the headache using it instead of the old raw SQL code? So far there are many constraints and it requires a higher learning curve.
Some confusing parts I have find online what is the difference between the context.Database.ExecuteSqlCommand and this MSDN http://msdn.microsoft.com/en-us/library/bb738684.aspx the code looks entirely different then my approach.
EDIT
I have used a different approach to insert the Date and Time while inserting all the info from the textbox.
using (var db = new ROGContext())
{
ProductDB product = new ProductDB
{
Material_No = long.Parse(MaterialNo_txtbox.Text),
Product_Line = ProductLineDropDownList1.SelectedItem.Text,
Product_Description = Description_txtbox.Text,
Size = Size_txtbox.Text,
UOM = UOM_txtbox.Text,
SupplierID = long.Parse(SupplierCountryListBox.SelectedItem.Value),
CreatedProduct_Date = DateTime.Parse(System.DateTime.Now.ToShortDateString()), //in the SQL database I have set the datatype as date to get yyyy/mm/dd
CreatedProduct_Time = DateTime.Now.TimeOfDay //in the SQL database I have set the datatype as time(0) to get hh:mm:ss
};
long queryselect = (from materialno in db.ProductDBs
where materialno.Material_No == product.Material_No
select materialno.Material_No).SingleOrDefault();
if (queryselect != long.Parse(materialnotxt))
{
Label1.Text = "Product successfully added in database";
Label1.Visible = true;
db.ProductDBs.Add(product);
db.SaveChanges();
}
You can use Context.ExecuteStoreCommand for Insert, Update and Delete.
See in Page 64 of Entity Framework 4.0 Recipes: A Problem-Solution Approach
Answer your edited part:
ExecuteStoreQuery for Select
ExecuteStoreCommand for Insert, Update and Delete
Entity Framework v4 – Tips and Tricks
this is a method i was reading about #MSDN ,
my question is if for an example i would like to use it on a stored procedure
with the fact that the query of that stored procedure is already specifying columns to select from the table like following :
SELECT Columnsome, columnother, , , , ...FROM thisSQLdbTable
though i would like to implement the approach of that specific method , it seems very advanced from a little research i have made on
"the best way" available to extract data from SQL Server into Asp.net DataTable.
public static DataTable GetCustomerData(string dataSetName,
string connectionString)
{
DataTable table = new DataTable(dataSetName);
using (SqlConnection connection = new SqlConnection(connectionString))
{
SqlDataAdapter adapter = new SqlDataAdapter(
"SELECT CustomerID, CompanyName, ContactName FROM dbo.Customers", connection);
DataTableMapping mapping = adapter.TableMappings.Add("Table", "Customers");
mapping.ColumnMappings.Add("CompanyName", "Name");
mapping.ColumnMappings.Add("ContactName", "Contact");
connection.Open();
adapter.FillSchema(table, SchemaType.Mapped);
adapter.Fill(table);
return table;
}
}
or is it not the method to use if i am querying via SP that specifies the selected column
i could actually drop that stored procedure if it is not requiered to select /specify columns
the stored procedure is doing a specific calculation and updates the table with results of calculation then i am switching it's "MODE" to select results from the table that was updated.
what i did is recyceling (; giving it a parameter (bit type)
stored procedure then asks for the value of supplied bool / bit Parameter,
if its is status true it updates (doing its original task it was made for)
if its false its doing a select oporation so i am using it as i would with 2 separated commands
but now that i have search for a better way to extract data from db into a Data table
i give up on the two way SP and i will make a selection via the exaple above if they're not intended to be used thogether as with my current SP that does preselection when servs the GetCustomersData() above.
So the question is do i need to let the function to make the selection or can i serve it with my sp ready made selection to implemet it with GetCustomersData() in the way that it will only do rest of task and only mapp the columns that was preselected
Still a bit confused on your actual requirement but here goes:
I See you are using a direct query in your C# code, 'best way' would be to make a SP out of it then say:
SqlCommand command = conn.CreateCommand();
SqlDataAdapter sqlAdapter = new SqlDataAdapter(command);
command.CommandType = System.Data.CommandType.StoredProcedure;
command.CommandText = "sp_GetCustomerData";
Then after you have added parameters if needed do:
conn.Open();
sqlAdapter.Fill(dtResult);
conn.Close();
Where dtResult is Datatable.
So you do not need to do any mapping in this case, and since you are using a SP from the Database it will work faster than your direct query and you can change the query logic any time without the need of re deploying your code.
Stored procedures are perfectly valid in this use case. however, if you want more of a properly mapped table, you have several options, some of which go beyond the use of DataTables.
You can use strongly typed DataSets or perhaps use an ORM (object relational mapper).
ref: Typed Datasets: http://msdn.microsoft.com/en-us/library/esbykkzb(v=vs.71).aspx
ref: What is an ORM : http://en.wikipedia.org/wiki/Object-relational_mapping
EXAMPLES OF ORM'S
ref: Entity Framework : http://msdn.microsoft.com/en-us/data/ef.aspx
ref: NHibernate: http://nhforge.org/