I'm changing my WPF application to use the Entity Framework instead of calling sql db directly.
On this one window I have a listview containing a gridview and I'm databinding it by using the following method which calls a stored procedure to get the data.
Now I already have my model generated from my existing sql database and included the stored proc...
How would I go about changing this method to read the data from the entity model instead of directly from sql?
public static void BindData(DataGrid grid)
{
SqlConnection loginCon = new SqlConnection();
loginCon.ConnectionString = ConfigurationManager.ConnectionStrings["ConString"].ConnectionString;
using (SqlDataAdapter adapter = new SqlDataAdapter("sp_SELECT_CONSHEAD", loginCon))
{
DataSet data = new DataSet();
adapter.Fill(data);
grid.ItemsSource = data.Tables[0].DefaultView;
}
}
You can use Function Import to get the stored procedure mapped to entity in EntityFramework. Then you can directly call the function in your code with single line of code.
grid.ItemsSource = dbContext.GetSP_Select_Conshead();
Related
I'm writing a new ASP.NET Core Web API, and one of my requirements is to be able to leverage EF Core 3.1 to grab the next value of a sequence defined in my SQL Server as the ID for a record I need to store.
I'm struggling to find a way to do this - in EF 6.x, I used a method directly on the DbContext descendant like this:
public int GetNextSequenceValue()
{
var rawQuery = Database.SqlQuery<int>("SELECT NEXT VALUE FOR dbo.TestSequence;");
var task = rawQuery.SingleAsync();
int nextVal = task.Result;
return nextVal;
}
and for EF Core up to 2.1, I would have been able to use Database.ExecuteSqlCommand() to run a SQL snippet and get back results. But it seems, in EF Core 3.x, I'm out of luck....
I know there are the .FromSqlRaw() and .FromSqlInterpolated methods on the DbSet - but since I only need to return the next value of a sequence (an INT), that's not going to fly. And I also know these methods also exist on the context.Database level which looks like it would be really close to what I had in EF 6.x - but here, those methods will only return the number of rows affected - I haven't found a way to send back the new value from the SEQUENCE.
Can it really be that in EF Core 3.x, I have to actually resort back to way-old ADO.NET code to fetch that value?? Is there REALLY no way to execute an arbitrary SQL snippet and get back some results from the context??
If you want to run an arbitrary TSQL batch and return a scalar value, you can do it like this:
var p = new SqlParameter("#result", System.Data.SqlDbType.Int);
p.Direction = System.Data.ParameterDirection.Output;
context.Database.ExecuteSqlRaw("set #result = next value for some_seq", p);
var nextVal = (int)p.Value;
Looks like executing raw SQL is not priority for EF Core, so up to now (EF Core 3.1) it's providing publicly just few basic limited methods. FromSql requires entity type or keyless entity type, and ExecuteSqlRaw / ExecuteSqlInterpolated are the "modern" bridge to ADO.NET ExecuteNonQuery which returns the affected rows.
The good thing is that EF Core is built on top of a public service architecture, so it can be used to add some missing functionalities. For instance, services can be used to build the so called IRelationalCommand, which has all the DbCommand execute methods, in particular ExecuteScalar needed for SQL in question.
Since EF Core model supports sequences, there is also a service for building the IRelationalCommand needed to retrieve the next value (used internally by HiLo value generators).
With that being said, following is a sample implementation of the custom method in question using the aforementioned concepts:
using System;
using System.Globalization;
using Microsoft.EntityFrameworkCore.Diagnostics;
using Microsoft.EntityFrameworkCore.Infrastructure;
using Microsoft.EntityFrameworkCore.Storage;
using Microsoft.EntityFrameworkCore.Update;
namespace Microsoft.EntityFrameworkCore
{
public static partial class CustomExtensions
{
public static long GetNextSequenceValue(this DbContext context, string name, string schema = null)
{
var sqlGenerator = context.GetService<IUpdateSqlGenerator>();
var sql = sqlGenerator.GenerateNextSequenceValueOperation(name, schema ?? context.Model.GetDefaultSchema());
var rawCommandBuilder = context.GetService<IRawSqlCommandBuilder>();
var command = rawCommandBuilder.Build(sql);
var connection = context.GetService<IRelationalConnection>();
var logger = context.GetService<IDiagnosticsLogger<DbLoggerCategory.Database.Command>>();
var parameters = new RelationalCommandParameterObject(connection, null, null, context, logger);
var result = command.ExecuteScalar(parameters);
return Convert.ToInt64(result, CultureInfo.InvariantCulture);
}
}
}
In your fluent api configs you can create migration that set ID automatically to be next value from Sequence
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.HasSequence<int>("OrderNumbers");
modelBuilder.Entity<Order>()
.Property(o => o.OrderNo)
.HasDefaultValueSql("NEXT VALUE FOR shared.OrderNumbers");
}
For creating sequence:
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.HasSequence<int>("OrderNumbers", schema: "shared")
.StartsAt(1000)
.IncrementsBy(5);
}
Read more from here: https://www.talkingdotnet.com/use-sql-server-sequence-in-entity-framework-core-primary-key/
For people suffering with oracle version of this problem, here's a solution:
var p = new OracleParameter("result", OracleDbType.Decimal, null, System.Data.ParameterDirection.Output);
Database.ExecuteSqlRaw($"BEGIN :result := my_seq.nextval; END;", p);
var nextVal = p.Value;
Ugly, but the best thing I could come up with:
var connection = repcontext.Database.GetDbConnection();
connection.Open();
using var cmd = connection.CreateCommand();
cmd.CommandText = "SELECT NEXT VALUE FOR AA.TransSeq;";
var obj = cmd.ExecuteScalar();
connection.Close();
seqnum = (int)obj;
This code should work in a variety of situations:
public static class DbSequence
{
private const string sqlCode = "SELECT NEXT VALUE FOR {0}.{1};";
public static T GetNextSeq<T>(this DbContext dbContext, string seqName)
{
var sqlCnn = dbContext.Database.GetDbConnection();
bool cnnClosed = sqlCnn.State != ConnectionState.Open;
if (cnnClosed) sqlCnn.Open();
try
{
using (var sqlCmd = sqlCnn.CreateCommand())
{
sqlCmd.Transaction = dbContext.Database.CurrentTransaction?.GetDbTransaction();
sqlCmd.CommandText = string.Format(sqlCode, "dbo", seqName);
var result = sqlCmd.ExecuteScalar();
if ((result == null) || (result == DBNull.Value)) throw new InvalidOperationException();
return (T)result;
}
}
finally
{
if (cnnClosed) sqlCnn.Close();
}
}
}
This code works when the connection is closed, opening it when needed and closing it after itself. It should also work when a transaction has been initiated. According to this source: https://learn.microsoft.com/en-us/sql/t-sql/statements/create-sequence-transact-sql?view=sql-server-ver16#general-remarks sequences run outside of transactions. Still, if it's available, I set up a transaction for the command. I also use generics and extension methods.
I am very new to linq and am trying to figure out how to accomplish the following:
Currently, I have a Winforms project that has a Base Form with a DataRow as one of it's members. I have several derived Forms populate the DataRow based on data from a DataTable (SQL Query Result). There are controls on the derived Forms that are populated with the values from the data as well. When the Save button on the derived Forms is clicked, the DataRow in the Base Form is updated and then the Derived Form updates the Database via a DataAdapter.
I wanted to replace all of the SQL Commands using linqs so I tried implementing this functionality using LINQ by the following:
I created my Linq query in the Derived Form and assigned the result to an Object in the Base Form. I cast the Object in the Base Form to the class type of the Linq query and use reflection to populate all the controls on the Derived Form. When the save button is clicked I update the Object but I am not able to update the Database.
The problem that I can't solve is how to update the database once the object is updated. At this point I don't have the Data Context that I used for the linq query.
I am using an SQL function within the linq query so I had to create a separate class for these values as I was getting an anonymous type error. I am probably missing something here.
Any help would be most appreciated as I really how clean the linq code is.
Edit (Copied from Brad's Edit to Tomas's answer):
Here are the 3 steps of my code.
Step 1 - Get a singe record of data from database
private void GetDatabaseDetailData()
{
_db = new PriorityDataContext();
DetailData = (from db in _db.tblDatabases
where db.DatabaseID == Id
select db).SingleOrDefault();
DeveloperData = (from db in _db.tblDatabases
where db.DatabaseID == Id
select new DeveloperInfo
{
DeveloperName = _db.func_get_employee_name(db.Developer)
}).SingleOrDefault();
}
Step 2 - Populate all controls whos name exists in the Object. The DetailData Object is cast to the specific type passed into this method. All code not shown for brevity.
protected virtual void PopulateDetailControlsA(List<Control> controlContainers, string srcDataTableName)
{
Object data = null;
Type type = null;
switch (srcDataTableName)
{
case "tblDatabases" :
type = typeof(tblDatabase);
data = (tblDatabase)DetailData;
break;
}
if (type != null)
{
var properties = type.GetProperties(BindingFlags.Public | BindingFlags.Instance);
foreach (var controlContainer in controlContainers)
{
foreach (var propertyInfo in properties)
{
if (!ControlExists(controlContainer, propertyInfo.Name)) continue;
var txtControl = controlContainer.Controls[propertyInfo.Name] as ExtendedTextBox;
if (txtControl != null)
{
try
{
var value = propertyInfo.GetValue(data, null).ToString();
if (propertyInfo.Name == "row_oper_name" || propertyInfo.Name == "row_last_chng_oper_name")
{
txtControl.Text = RowOperatorData.RowOperatorName;
txtControl.ValueMember = propertyInfo.GetValue(data, null).ToString();
}
else
txtControl.Text = value;
}
catch (NullReferenceException)
{
}
continue;...........
Step 3 - Try and save changes back to database in the derived From.
private void SaveData()
{
try
{
_db.SubmitChanges();
}
catch (Exception sqlException)
{
}
}
What I am really unclear about hear is how to store the result set in the Base Form so that I can use the same code for many different queries. The DataRow worked great because I use the some code for over 25 derive Forms.
If I understand you correctly, you create the DataContext in a derived form and then use it to write some queries (in a derived form). In order to be able to update the database, your queries must return the entities obtained from the table (i.e. the select clause should just return the entity). For example:
DataContext db = // ...
var q = from p in db.Things
where p.Some > 10 select p;
If you then modify the entities, you can use db.SubmitChanges() to store the changes (made to the entity objects) to the database. For this, you need the original db value.
In your scenario, you'll need to store the DataContext (as a field) in the derived form. If you need to perform the update from the base form, then I suggest you define a virtual method:
// Base form
protected abstract void UpdateDatabase();
// Derived from with field 'db' storing 'DataContext'
protected override void UpdateDatabase() {
db.SumbitChanges();
}
I'm using a BindingList to display a list of Person objects in a DataGridView in a Windows Forms application. Changes to the DataGridView change the underlying BindingList. I've got this part working.
Now I want the list persisted to a database table. Reading the list from the database and populating the Person list is straight forward, but if I add/edit/delete a person from the DataGridView, how and when do I persist that change back to the database?
(Secondly, is this approach okay or am I missing some bigger picture? I don't want to use data tables because I want to work with my code in an abstracted object oriented way.)
For easy persistence of objects in Windows Forms for a start you can use LINQ2SQL, it does exactly what you want plus also materializes objects when you want to gather them from database.
Quick example, after you create linq context from database schema for supported databases, which is SQL Server (Express), all you need is to create it's instance in your form and use it during single atomic operation with data - read, edit, write or cancel.
private YourAppContext context;
private void RenewContext()
{
context = new YourAppContext();
}
private void LoadData()
{
RenewContext();
DataGridView1.DataSource = context.Articles.OrderByDescending(x => x.DatePosted).Take(10);
}
private void AcceptButtonPressed()
{
context.SubmitChanges();
}
private void CancelButtonPressed()
{
LoadData();
}
Obviously you can pass your data through BindingSource.
I want to execute a custom command against a typed dataset I created using the dataset designer. For this I need to get a reference to the underlying connection, right? How to go about this? In which autogenerated file can I find the connection?
You can set the ConnectionModifier property of the TableAdapter in the designer, is defaulted to Internal, so you can use it in the same project/assembly, change it to Public and use it everywhere you need it. Or a better aproach will be create a partial class based in your TableAdapter name/namespace and encapsulate the logic within the same table adapter:
// if DataSet name is Sales and Table name is Order
namespace SalesTableAdapters // use full namespace here
{
public partial class OrderTableAdapter
{
public void CustomCommand()
{
// here you can use the property this.Connection
// and execute your command
}
}
}
typedTableAdapter ta = new myNameSpace.myDataSet.myDataSetTableAdapters.typedTableAdapter;
SqlClient.SqlCommand com = new SqlClient.SqlCommand("my query");
com.Connection = ta.Connection;
I have a grid bound to a BindingSource which is bound to DataContext table, like this:
myBindingSource.DataSource = myDataContext.MyTable;
myGrid.DataSource = myBindingSource;
I couldn't refresh BindingSource after insert. This didn't work:
myDataContext.Refresh(RefreshMode.OverwriteCurrentValues, myBindingSource);
myBindingSource.ResetBinding(false);
Neither this:
myDataContext.Refresh(RefreshMode.OverwriteCurrentValues, myDataContext.MyTable);
myBindingSource.ResetBinding(false);
What should I do?
I have solved the problem but not in a way I wanted.
Turns out that DataContext and Linq To SQL is best for unit-of-work operations. Means you create a DataContext, get your job done, discard it. If you need another operation, create another one.
For this problem only thing I had to do was recreate my DataContext like this.dx = new MyDataContext();. If you don't do this you always get stale/cached data. From what I've read from various blog/forum posts that DataContext is lightweight and doing this A-OK. This was the only way I've found after searching for a day.
And finally one more working solution.
This solution works fine and do not require recreating DataContext.
You need to reset internal Table cache.
for this you need change private property cachedList of Table using reflection.
You can use following utility code:
public static class LinqDataTableExtension
{
public static void ResetTableCache(this ITable table)
{
table.InternalSetNonPublicFieldValue("cachedList", null);
}
public static void ResetTableCache(this IListSource source)
{
source.InternalSetNonPublicFieldValue("cachedList", null);
}
public static void InternalSetNonPublicFieldValue(this object entity, string propertyName, object value)
{
if (entity == null)
throw new ArgumentNullException("entity");
if(string.IsNullOrEmpty(propertyName))
throw new ArgumentNullException("propertyName");
var type = entity.GetType();
var prop = type.GetField(propertyName, BindingFlags.NonPublic | BindingFlags.Instance);
if (prop != null)
prop.SetValue(entity, value);
// add any exception code here if property was not found :)
}
}
using something like:
var dSource = Db.GetTable(...)
dSource.ResetTableCache();
You need to reset your BindingSource using something like:
_BindingSource.DataSource = new List();
_BindingSource.DataSource = dSource;
// hack - refresh binding list
Enjoy :)
Grid Data Source Referesh by new query instead just Contest.Table.
Simple Solution < But Working.
Whre is eg.
!!!!! Thanks - Problem Solved after no of days !!! but with so simple way ..
CrmDemoContext.CrmDemoDataContext Context = new CrmDemoContext.CrmDemoDataContext();
var query = from it in Context.Companies select it;
// initial connection
dataGridView1.DataSource = query;
after changes or add in data
Context.SubmitChanges();
//call here again
dataGridView1.DataSource = query;
I have the same problem. I was using a form to create rows in my table without saving the context each time. Luckily I had multiple forms doing this and one updated the grid properly and one didn't.
The only difference?
I bound one to the entity similarly (not using the bindingSource) to what you did:
myGrid.DataSource = myDataContext.MyTable;
The second I bound:
myGrid.DataSource = myDataContext.MyTable.ToList();
The second way worked.
I think you should also refresh/update datagrid. You need to force redraw of grid.
Not sure how you insert rows. I had same problem when used DataContext.InsertOnSubmit(row), but when I just inserted rows into BindingSource instead BindingSource.Insert(Bindingsource.Count, row)
and used DataContext only to DataContext.SubmitChanges() and DataContext.GetChangeSet(). BindingSource inserts rows into both grid and context.
the answer from Atomosk helped me to solve a similar problem -
thanks a lot Atomosk!
I updated my database by the following two lines of code, but the DataGridView did not show the changes (it did not add a new row):
this.dataContext.MyTable.InsertOnSubmit(newDataset);
this.dataContext.SubmitChanges();
Where this.dataContext.MyTable was set to the DataSource property of a BindingSource object, which was set to the DataSource property of a DataGridView object.
In code it does looks like this:
DataGridView dgv = new DataGridView();
BindingSource bs = new BindingSource();
bs.DataSource = this.dataContext.MyTable; // Table<T> object type
dgv.DataSource = bs;
Setting bs.DataSource equals null and after that back to this.dataContext.MyTable did not help to update the DataGridView either.
The only way to update the DataGridView with the new entry was a complete different approach by adding it to the BindingSource instead of the corresponding table of the DataContext, as Atomosk mentioned.
this.bs.Add(newDataset);
this.dataContext.SubmitChanges();
Without doing so bs.Count; returned a smaller number as this.dataContext.MyTable.Count();
This does not make sense and seems to be a bug in the binding model in my opinion.