I am using entity framework database raw query.
using var command = context.Database.GetDbConnection().CreateCommand();
command.CommandText = "select * from my_school";
using var dataReader = command.ExecuteReader();
var dataRow = ReadSchools(dataReader);
command.Connection.Close();????
After dataReader read the result, should I close the connection or does using statement close the connection after scope? If I don't close, does the connection pool fill?
You can use using for DBConnection as following:
using (var conn = context.Database.GetDbConnection())
{
var command = conn.CreateCommand();
command.CommandText = "select * from my_school";
var dataReader = command.ExecuteReader();
var dataRow = ReadSchools(dataReader);
}
For more detail please check Working with DbContext
i have a function which is called on form load
it should retrieve some data from a view and fill the dataset
but when it reaches the da.Fill(ds); line, all of the code below it (including itself) is awkwardly jumped
then form loads and my function becomes useless
below is the body of my function
SqlConnection conn = create_conn();
conn.Open();
SqlCommand cmd = new SqlCommand("View1", conn);
cmd.CommandType = System.Data.CommandType.StoredProcedure;
cmd.Parameters.Add("keyfield", System.Data.SqlDbType.Char).Value = keyfieldval;
SqlDataAdapter da = new SqlDataAdapter();
da.SelectCommand = cmd;
DataSet ds = new DataSet();
da.Fill(ds); // <--- THIS IS THE LINE
Form1.field1 = ds.Tables[0].Rows[0]["field1"].ToString();
Form1.field2 = ds.Tables[0].Rows[0]["field2"].ToString();
conn.Close();
I am trying to read an XPS file that I have inserted into my database using the Filestream attribute. Here is my code thus far.
RewardsDataContext dx = new RewardsDataContext();
var img = (from c in dx.RwProductsTests
select c).FirstOrDefault();
byte[] buffer = img.Blob.ToArray();
MemoryStream ms = new MemoryStream();
ms.Write(buffer, 0, buffer.Length);
ms.Position = 0;
Package package = Package.Open(ms, FileMode.OpenOrCreate, FileAccess.ReadWrite);
XpsDocument MyDoc = new XpsDocument(package);
dv1.Document = MyDoc.GetFixedDocumentSequence();
dx.Dispose();
and I get the following error.
XpsDocument URI is null. Use XpsDocument constructor that takes URI parameter.
I am working with a system that has many stored procedures that need to be displayed. Creating entities for each of my objects is not practical.
Is it possible and how would I return a DataTable using ExecuteStoreQuery ?
public ObjectResult<DataTable> MethodName(string fileSetName) {
using (var dataContext = new DataContext(_connectionString))
{
var returnDataTable = ((IObjectContextAdapter)dataContext).ObjectContext.ExecuteStoreQuery<DataTable>("SP_NAME","SP_PARAM");
return returnDataTable;
}
Yes it's possible, but it should be used for just dynamic result-set or raw SQL.
public DataTable ExecuteStoreQuery(string commandText, params Object[] parameters)
{
DataTable retVal = new DataTable();
retVal = context.ExecuteStoreQuery<DataTable>(commandText, parameters).FirstOrDefault();
return retVal;
}
Edit: It's better to use classical ADO.NET to get the data model rather than using Entity Framework because most probably you cannot use DataTable even if you can run the method: context.ExecuteStoreQuery<DataTable>(commandText, parameters).FirstOrDefault();
ADO.NET Example:
public DataSet GetResultReport(int questionId)
{
DataSet retVal = new DataSet();
EntityConnection entityConn = (EntityConnection)context.Connection;
SqlConnection sqlConn = (SqlConnection)entityConn.StoreConnection;
SqlCommand cmdReport = new SqlCommand([YourSpName], sqlConn);
SqlDataAdapter daReport = new SqlDataAdapter(cmdReport);
using (cmdReport)
{
SqlParameter questionIdPrm = new SqlParameter("QuestionId", questionId);
cmdReport.CommandType = CommandType.StoredProcedure;
cmdReport.Parameters.Add(questionIdPrm);
daReport.Fill(retVal);
}
return retVal;
}
No, I don't think that'll work - Entity Framework is geared towards returning entities and isn't meant to return DataTable objects.
If you need DataTable objects, use straight ADO.NET instead.
This method uses the connection string from the entity framework to establish an ADO.NET connection, to a MySQL database in this example.
using MySql.Data.MySqlClient;
public DataSet GetReportSummary( int RecordID )
{
var context = new catalogEntities();
DataSet ds = new DataSet();
using ( MySqlConnection connection = new MySqlConnection( context.Database.Connection.ConnectionString ) )
{
using ( MySqlCommand cmd = new MySqlCommand( "ReportSummary", connection ) )
{
MySqlDataAdapter adapter = new MySqlDataAdapter( cmd );
adapter.SelectCommand.CommandType = CommandType.StoredProcedure;
adapter.SelectCommand.Parameters.Add( new MySqlParameter( "#ID", RecordID ) );
adapter.Fill( ds );
}
}
return ds;
}
Yes it can easily be done like this:
var table = new DataTable();
using (var ctx = new SomeContext())
{
var cmd = ctx.Database.Connection.CreateCommand();
cmd.CommandText = "Select Col1, Col2 from SomeTable";
cmd.Connection.Open();
table.Load(cmd.ExecuteReader());
}
By the rule, you shouldn't use a DataSet inside a EF application. But, if you really need to (for instance, to feed a report), that solution should work (it's EF 6 code):
DataSet GetDataSet(string sql, CommandType commandType, Dictionary<string, Object> parameters)
{
// creates resulting dataset
var result = new DataSet();
// creates a data access context (DbContext descendant)
using (var context = new MyDbContext())
{
// creates a Command
var cmd = context.Database.Connection.CreateCommand();
cmd.CommandType = commandType;
cmd.CommandText = sql;
// adds all parameters
foreach (var pr in parameters)
{
var p = cmd.CreateParameter();
p.ParameterName = pr.Key;
p.Value = pr.Value;
cmd.Parameters.Add(p);
}
try
{
// executes
context.Database.Connection.Open();
var reader = cmd.ExecuteReader();
// loop through all resultsets (considering that it's possible to have more than one)
do
{
// loads the DataTable (schema will be fetch automatically)
var tb = new DataTable();
tb.Load(reader);
result.Tables.Add(tb);
} while (!reader.IsClosed);
}
finally
{
// closes the connection
context.Database.Connection.Close();
}
}
// returns the DataSet
return result;
}
In my Entity Framework based solution I need to replace one of my Linq queries with sql - for efficiency reasons.
Also I want my results in a DataTable from one stored procedure so that I could create a table value parameter to pass into a second stored procedure. So:
I'm using sql
I don't want a DataSet
Iterating an IEnumerable probably isn't going to cut it - for efficiency reasons
Also, I am using EF6, so I would prefer DbContext.SqlQuery over ObjectContext.ExecuteStoreQuery as the original poster requested.
However, I found that this just didn't work:
_Context.Database.SqlQuery<DataTable>(sql, parameters).FirstOrDefault();
This is my solution. It returns a DataTable that is fetched using an ADO.NET SqlDataReader - which I believe is faster than a SqlDataAdapter on read-only data. It doesn't strictly answer the question because it uses ADO.Net, but it shows how to do that after getting a hold of the connection from the DbContext
protected DataTable GetDataTable(string sql, params object[] parameters)
{
//didn't work - table had no columns or rows
//return Context.Database.SqlQuery<DataTable>(sql, parameters).FirstOrDefault();
DataTable result = new DataTable();
SqlConnection conn = Context.Database.Connection as SqlConnection;
if(conn == null)
{
throw new InvalidCastException("SqlConnection is invalid for this database");
}
using (SqlCommand cmd = new SqlCommand(sql, conn))
{
cmd.Parameters.AddRange(parameters);
conn.Open();
using (SqlDataReader reader = cmd.ExecuteReader())
{
result.Load(reader);
}
return result;
}
}
The easiest way to return a DataTable using the EntityFramework is to do the following:
MetaTable metaTable = Global.DefaultModel.GetTable("Your EntitySetName");
For example:
MetaTable metaTable = Global.DefaultModel.GetTable("Employees");
Maybe your stored procedure could return a complex type?
http://blogs.msdn.com/b/somasegar/archive/2010/01/11/entity-framework-in-net-4.aspx
I need to learn ADO.NET to build applications based on MS Office. I have read a good deal about ADO.NET in the MSDN Library, but everything seems rather messy to me.
What are the basics one must figure out when using ADO.NET? I think a few key words will suffice to let me organize my learning.
There are three key components (assuming ur using SQL server):
SQLConnection
SqlCommand
SqlDataReader
(if you're using something else, replace Sql with "Something", like MySqlConnection, OracleCommand)
Everything else is just built on top of that.
Example 1:
using (SqlConnection connection = new SqlConnection("CONNECTION STRING"))
using (SqlCommand command = new SqlCommand())
{
command.commandText = "SELECT Name FROM Users WHERE Status = #OnlineStatus";
command.Connection = connection;
command.Parameters.Add("#OnlineStatus", SqlDbType.Int).Value = 1; //replace with enum
connection.Open();
using (SqlDataReader dr = command.ExecuteReader))
{
List<string> onlineUsers = new List<string>();
while (dr.Read())
{
onlineUsers.Add(dr.GetString(0));
}
}
}
Example 2:
using (SqlConnection connection = new SqlConnection("CONNECTION STRING"))
using (SqlCommand command = new SqlCommand())
{
command.commandText = "DELETE FROM Users where Email = #Email";
command.Connection = connection;
command.Parameters.Add("#Email", SqlDbType.VarChar, 100).Value = "user#host.com";
connection.Open();
command.ExecuteNonQuery();
}
Another way of getting a command object is to call connection.CreateCommand().
That way you shouldn't have to set the Connection property on the command object.