How is it done using the ObjectQuery method?
You can always attach something to the .Log property of your DataContext. That will show all the SQL commands as they are sent.
I do this in my base for data access objects and output it to the Visual Studio debug console. As the objects create their DataContext I check it see if its debug and attach a TextWritter helper class like this:
dbDataContext _dB = new dbDataContext();
_dB.CommandTimeout = 5000;
#if DEBUG
_dB.Log = new DebugTextWriter();
#endif
Here is the helper object for output to the debug console:
//utility class for output of TextWriter for the Visual Sudio Debug window
class DebugTextWriter : System.IO.TextWriter
{
public override void Write(char[] buffer, int index, int count)
{
System.Diagnostics.Debug.Write(new String(buffer, index, count));
}
public override void Write(string value)
{
System.Diagnostics.Debug.Write(value);
}
public override Encoding Encoding
{
get { return System.Text.Encoding.Default; }
}
}
Here is what I found using ObjectQuery Method. Using console for testing, you can do the following:
Create an Extension Method as below, then call it. Say Product product, then SQL prints out as product.ToTraceString.
public static class MyExtensions
{
public static string ToTraceString<T>(this IQueryable<T> t)
{
string sql = "";
ObjectQuery<T> oqt = t as ObjectQuery<T>;
if (oqt != null)
sql = oqt.ToTraceString();
return sql;
}
}
You could have a look at the Linq-to-SQL Debug Visualizer, or just hover your mouse over your Linq-to-SQL query (tooltip should show generated SQL), or access:
context.GetCommand(query).CommandText
var q = from img in context.Images
...
select img;
string sql = q.ToString();
sql will contain the sql select query.
EDIT: disadvantage: parameters won't have any values at this time
You could run the SQL Server Profiler.
This is what I use when setting up the database context:
this.DbContext.Database.Log += s => Debug.WriteLine(s);
just a small update you can now use an Action to log the SQL:
// test SQL logger
Action<string> SQLLogger = (message) => System.Diagnostics.Debug.Write(message);
_dB.Context().Database.Log = SQLLogger;
If you are executing the linq query against a database, you can run the SQL Profiler to record the SQL query that is being executed. We do it quite often to identify any performance impact on conversion.
Related
I am new to Web API, Entity Framework and OData. I asked a similar question in another forum but haven't gotten a relevant response.
We have a OData compliant web api service for use in Salesforce. We have a custom complex query in Oracle that we need to expose.
I am not sure how to use a custom query like we want to also allow for odata parameter filtering to occur? ($filter, $top, $skip, etc) For example, when a $filter is used i want to apply that filter to the custom query and then send it back to the database to have it return the result set. How can i do this?
The issue i seem to have is that I can see the parameters as they come in but they are not translating to the query being passed to oracle. It seems that it will fire the query returning the full result set and then apply the parameters. This is very slow as the result set is very large.
I am hoping 2 figure out 2 things
1. How can i use custom sql and apply odata parameters to the underlying query?
2. When using EF or a custom query, how can i apply odata parameters to the query so that when the query is sent to the database that the $filter parameter, for example, is included in the query? I don't want the full result returned then apply the filter.
Can anyone give me some pointers on how to make this happen?
private static ODataValidationSettings _validationSettings = new ODataValidationSettings();
//public IHttpActionResult GetName()
//{ }
// GET: odata/ShareData
[ODataRoute("Orders")]
[EnableQuery(PageSize = 50)]
public IHttpActionResult GetOrders(ODataQueryOptions<Orders> queryOptions)
{
// validate the query.
try
{
queryOptions.Validate(_validationSettings);
}
catch (ODataException ex)
{
return BadRequest(ex.Message);
}
try
{
string connectionString = ConfigurationManager.ConnectionStrings["DNATestConnectionString"].ConnectionString;
var items = GetDataItems(connectionString);
return Ok<IEnumerable<Orders>>(items);
}
catch (Exception ex)
{
return StatusCode(HttpStatusCode.InternalServerError);
}
}
#region Load Data Methods
private static List<Orders> GetDataItems(string connectionString)
{
List<Orders> items = new List<Orders>();
using (OracleConnection con = new OracleConnection(connectionString))
{
con.Open();
using (OracleCommand cmd = con.CreateCommand())
{
cmd.CommandText = "select po_header_id, segment1, vendor_id, vendor_site_id from po_headers_all where vendor_id=4993";
using (OracleDataReader rdr = cmd.ExecuteReader())
{
while (rdr.Read())
items.Add(ToOrders(rdr));
}
}
}
return items;
}
private static Orders ToOrders(OracleDataReader rdr)
{
Orders data = new Orders();
data.VENDOR_ID = ToInt32(rdr, "VENDOR_ID");
data.VENDOR_SITE_ID = ToInt32(rdr, "VENDOR_SITE_ID");
data.PO_HEADER_ID = ToInt32(rdr, "PO_HEADER_ID");
data.SEGMENT1 = Convert.ToString(rdr["SEGMENT1"]);
return data;
}
private static int ToInt32(OracleDataReader rdr, string name)
{
int index = rdr.GetOrdinal(name);
return rdr.IsDBNull(index) ? 0 : Convert.ToInt32(rdr[index]);
}
#endregion
I don't think this is possible.
How can i use custom sql and apply odata parameters to the underlying query?
As far as I'm aware, you can't. The whole point of the OData library is that it needs to work off an IQueryable. By using custom SQL in a string like you have in your example, you can't combine it with the OData parameters that are being passed in.
One approach would be to have your custom SQL in a SQL view, then add the SQL view to your EF model in the same way as you would add a table - it will be represented as a DbSet just like tables are.
You can then get an IQueryable to represent the dataset and then apply the OData parameters as follows:
public IHttpActionResult GetOrders(ODataQueryOptions<OrdersView> queryOptions)
{
IQueryable<OrdersView> allData = // ... get the DbSet from entity framework...
// this will apply the OData query to the data set and only pull the data you want from the database
var filteredResults = queryOptions.ApplyTo(allData) as IQueryable<OrdersView>;
return Ok<IQueryable<OrdersView>>(filteredResults);
}
I'm trying out Dapper with Oracle and I was trying to run a multi-resultset query but Oracle requires a dbtype of refcursor.
StringBuilder query = new StringBuilder("BEGIN ");
query.Append("OPEN :rs1 FOR SELECT * FROM Table1 where key=:KEY; ");
query.Append("OPEN :rs2 FOR SELECT * FROM Table2 where key=:KEY; ");
query.Append("END;");
Is there a way to pass an OracleParameter (maybe as DbParameter?) to Dapper? When I tried, it threw an error.
What is the advantage of using the DynamicParameter vs. using a DbParameter (assuming types are known etc.)?
A new interface was added in the most recent build that allows more control over the parameter - it was added to support TVPs in SQL server, but should work in this scenario. However, I'm also fairly content to add special casing for any types that look like dbparameter - and add them directly, which would allow you to add an oracleparameter directly.
DynamicParameters is about how many parameters to add, so it is a bit orthogonal to the value vs DbParameter discussion. At the moment, the code generally prefers to take control of adding parameters itself, so the caller just knows "an int named id with value 7" - not any ado.net details. But it could do.
Edit: if you really want to work with lists-of-parameters (i.e. List<DbParameter> etc), then you can do that with something like:
public class DbParams : Dapper.SqlMapper.IDynamicParameters,
IEnumerable<IDbDataParameter>
{
private readonly List<IDbDataParameter> parameters =
new List<IDbDataParameter>();
public IEnumerator<IDbDataParameter> GetEnumerator() {
return parameters.GetEnumerator(); }
IEnumerator IEnumerable.GetEnumerator() { return GetEnumerator(); }
public void Add(IDbDataParameter value)
{
parameters.Add(value);
}
void Dapper.SqlMapper.IDynamicParameters.AddParameters(IDbCommand command,
Dapper.SqlMapper.Identity identity)
{
foreach (IDbDataParameter parameter in parameters)
command.Parameters.Add(parameter);
}
}
with usage like:
public void TestCustomParameters()
{
var args = new DbParams {
new SqlParameter("foo", 123),
new SqlParameter("bar", "abc")
};
var result = connection.Query("select Foo=#foo, Bar=#bar", args).Single();
int foo = result.Foo;
string bar = result.Bar;
foo.IsEqualTo(123);
bar.IsEqualTo("abc");
}
which passes the test.
However, I must stress that I would prefer not to encumber the calling code with db-parameter knowledge unless it really really needs to know; I would by-far prefer:
var args = new {
foo = 123, bar = "abc"
};
which does exactly the same thing, but without dropping to ADO.NET; this can be especially important if you are using a "decorated" ADO.NET connection (for example, mini-profiler) - in which case the layer you get is not an OracleCommand / OracleConnection etc - it is abstracted. This means that forcibly adding an OracleParameter may not always work - but adding a parameter with name "foo" and value 123 - that is pretty reliable.
I know there is a way to use Expressions and Lambdas to accomplish this but I having a hard time piecing it all together. All I need is a method that will dynamically query an Entity Framework DBSet object to find the row where the propery with the given name matches the value.
My context:
public class MyContext : DbContext
{
public IDbSet<Account> Accoounts{ get { return Set<Account>(); } }
}
The method that I'm looking to write:
public T Get<T>(string property, object value) : where T is Account
{...}
I would rather not have to use Dynamic SQL to accomplish this so no need to suggest it because I already know it's possible. What I'm really looking for is some help to accomplish this using Expressions and Lambdas
Thanks in advance, I know it's brief but it should be pretty self-explanatory. Comment if more info is needed
I'm trying to avoid dynamic linq as much as possible because the main point of linq is strongly typed access. Using dynamic linq is a solution but it is exactly the oppose of the linq purpose and it is quite close to using ESQL and building the query from sting concatenation. Anyway dynamic linq is sometimes real time saver (especially when it comes to complex dynamic ordering) and I successfully use it in a large project with Linq-to-Sql.
What I usually do is defining some SearchCriteria class like:
public class SearchCriteria
{
public string Property1 { get; set; }
public int? Property2 { get; set; }
}
And helper query extension method like:
public static IQueryable<SomeClass> Filter(this IQueryable<SomeClass> query, SearchCriteria filter)
{
if (filter.Property1 != null) query = query.Where(s => s.Property1 == filter.Property1);
if (filter.Property2 != null) query = query.Where(s => s.Property2 == filter.Property2);
return query;
}
It is not generic solution. Again generic solution is for some strongly typed processing of classes sharing some behavior.
The more complex solution would be using predicate builder and build expression tree yourselves but again building expression tree is only more complex way to build ESQL query by concatenating strings.
Here's my implementation:
public T Get<T>(string property, object value) : where T is Account
{
//p
var p = Expression.Parameter(typeof(T));
//p.Property
var propertyExpression = Expression.Property(p, property);
//p.Property == value
var equalsExpression = Expression.Equal(propertyExpression, Expression.Constant(value));
//p => p.Property == value
var lambda = Expression.Lambda<Func<T,bool>>(equalsExpression, p);
return context.Set<T>().SingleOrDefault(lambda);
}
It uses EF 5's Set<T>() method. If you are using a lower version, you'll need to implement a way of getting the DbSet based on the <T> type.
Hope it helps.
Dynamic Linq may be an option. Specify your criteria as a string and it will get built as an expression and ran against your data;
An example from something I have done;
var context = new DataContext(ConfigurationManager.ConnectionStrings["c"].ConnectionString);
var statusConditions = "Status = 1";
var results = (IQueryable)context.Contacts.Where(statusConditions);
http://weblogs.asp.net/scottgu/archive/2008/01/07/dynamic-linq-part-1-using-the-linq-dynamic-query-library.aspx
I have queries that are built like this:
public static List<MyObjectModel> GetData (int MyParam)
{
using (DataModel MyModelDC = new DataModel())
{ var MyQuery = from....
select MyObjectModel { ...}
}
return new List<MyObjectModel> (MyQuery)
}
}
It seems that using compiled linq-to-sql queries are about as fast as stored procedures and so the goal is to convert these queries into compiled queries. What's the syntax for this?
Thanks.
Put something like this inside of your DataContext (or in your case your "DataModel"):
private static Func<DataModel, int, MyObjectModel> _getObjectModelById =
CompiledQuery.Compile<DataModel, int, MyObjectModel>(
(dataModel, myParam) =>
dataModel.PersonDtos.where(c => c.ObjectModelId == myParam).FirstOrDefault()
);
Then add amethod in there to call it like this:
internal List<MyObjectModel> GetObjectModel(int myParam)
{
var results = _getObjectModelById(this, myParam);
return results.SingleOrDefault();
}
Inside of your repository where your original method was call the internal function to get the result you are looking for.
Hope this helps -> I can post more code if necessary :)
I have IQueryable object and I need to take the data inside the IQueryable to put it into Textboxs controls. Is this possible?
I try something like:
public void setdata (IQueryable mydata)
{
textbox1.text = mydata.????
}
Update:
I'm doing this:
public IQueryable getData(String tableName, Hashtable myparams)
{
decimal id = 0;
if (myparams.ContainsKey("id") == true)
id = (decimal)myparams["id"];
Type myType= Type.GetType("ORM_Linq." + tableName + ", ORM_Linq");
return this.GetTable(tableName , "select * from Articu where id_tipo_p = '" + id + "'");
}
public IQueryable<T> GetTable<T>(System.Linq.Expressions.Expression<Func<T, bool>> predicate) where T : class
{
return _datacontext.GetTable<T>().Where(predicate);
}
This returns a {System.Data.Linq.SqlClient.SqlProvider+OneTimeEnumerable1[ORM_Linq.Articu]}`
I don't see any method like you tell me. I see Cast<>, Expression, ToString...
EDIT: Updated based on additional info from your other posts...
Your getData method is returning IQueryable instead of a strongly typed result, which is why you end up casting it. Try changing it to:
public IQueryable<ORM_Linq.Articu> getData(...)
Are you trying to query for "Articu" from different tables?
With the above change in place, your code can be rewritten as follows:
ORM_Linq.Articu result = mydata.SingleOrDefault();
if (result != null)
{
TextBoxCode.Text = result.id.ToString();
TextBoxName.Text = result.descrip;
}
If you have a single result use SingleOrDefault which will return a default value if no results are returned:
var result = mydata.SingleOrDefault();
if (result != null)
{
textbox1.text = result.ProductName; // use the column name
}
else
{
// do something
}
If you have multiple results then loop over them:
foreach (var item in mydata)
{
string name = item.ProductName;
int id = item.ProductId;
// etc..
}
First, you should be using a strongly-typed version of IQueryable. Say that your objects are of type MyObject and that MyObject has a property called Name of type string. Then, first change the parameter mydata to be of type IQueryable<MyObject>:
public void setdata (IQueryable<MyObject> mydata)
Then we can write a body like so to actually get some data out of. Let's say that we just want the first result from the query:
public void setdata (IQueryable<MyObject> mydata) {
MyObject first = mydata.FirstOrDefault();
if(first != null) {
textbox1.Text = first.Name;
}
}
Or, if you want to concatenate all the names:
public void setdata(IQueryable<MyObject> mydata) {
string text = String.Join(", ", mydata.Select(x => x.Name).ToArray());
textbo1.Text = text;
}
Well, as the name suggests, an object implementing IQueryable is... Queryable! You'll need to write a linq query to get at the internal details of your IQueryable object. In your linq query you'll be able to pull out its data and assign bits of it where ever you'd like - like your text box.
Here's a great starting place for learning Linq.
I think you find the same mental struggle when coming from FoxPro and from DataSet. Really nice, powerful string-based capabilities(sql for query, access to tables and columns name) in these worlds are not available, but replaced with a compiled, strongly-typed set of capabilities.
This is very nice if you are statically defining the UI for search and results display against a data source known at compile time. Not so nice if you are trying to build a system which attaches to existing data sources known only at runtime and defined by configuration data.
If you expect only one value just call FirstOrDefault() method.
public void setdata (IQueryable mydata)
{
textbox1.text = mydata.FirstOrDefault().PropertyName;
}