I am scratching my head here. I have a bootstrap modal that has a field for entering in a sql query. The query I pass uses an AJAX call to a controller and executes the sql query using the code below and returns a JSON object. Something like this:
context.Database.SqlQuery(typeof(object), query);
But all I get are empty objects. I can't pass a type when I don't know the columns. For instance I could do something like this:
public class CusType {
public CusType(){}
public int Id { get; set; }
public string Name { get; set; }
}
and then do something like this:
context.Database.SqlQuery(typeof(CusType), query);
But that won't help me when I don't know or can't know the columns. I even tried an idea using ExpandoObjects. Example:
List<string> columns = new List<string>();
string tmpCol = query;
string[] seperator = new string[] { "from" };
tmpCol = query.ToLower()
.Replace(#"\s+", "")
.Replace("select", "");
tmpCol = tmpCol.Split(seperator, 1, StringSplitOptions.RemoveEmptyEntries)[0];
for (int i = 0; i < tmpCol.Split(',').Length; i++)
{
columns.Add(tmpCol.Split(',')[i]);
}
dynamic data = new ExpandoObject();
IDictionary<string, object> props = (IDictionary<string, object>)data;
foreach (var column in columns)
{
props.Add(column.ToString(), column.ToString());
}
return context.Database.SqlQuery(data.GetType(), query);
But what do I do when I want to execute the query?
context.Database.SqlQuery(data.GetType()??, query);
Even when I do put in the data.GetType() it returns empty objects.
In both examples (using typeof(object) and typeof(data.GetType()) I get this JSON object returned:
[{},{},{},{},{},{},{},{},{},{},{},{},{}]
Any ideas/suggestions?
Entity Framework populates a model based on the type specified. You'll need to use something else or go old school with a DataReader.
Related
I am working on connecting to SQL database and setting variables in my C# application to match returned values from a Dapper Query.
I am able to return the correct row information (I used a datagridview to show that i get the correct row, and when i debug i see the right data) but how do I set a program variable to just one of the columns? here is some code showing my process
Connect & run stored procedure:
using (SqlConnection conn = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["MfgDataCollector"].ToString()))
{
DynamicParameters param = new DynamicParameters();
param.Add("#UserID", txt_userid.Text.Trim());
List<User> userinfo = conn.Query<User>("GetUserInfo", param, commandType: CommandType.StoredProcedure).ToList<User>();
Variables.UserID = txt_userid.Text.Trim();
datagridview1.DataSource = userinfo; //this displays the right information, however I want to store the information as a public variable(like above)
Variables.Userfull = userinfo; //when debugging this shows I have the right information but its all columns of user
User Class:
class User
{
public string UserID { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public int AccessLevel { get; set; }
public int FirstUse { get; set; }
public string Password { get; set; }
public int LoginCounter { get; set; }
public string LastLogin { get; set; }
public string FirstLogin { get; set; }
public string UserFullName { get; set; }
}
EDIT
per answer, I have tried to switch the command to executescalar with this code:
var userinfo = conn.ExecuteScalar<User>("GetUserInfo", param, commandType: CommandType.StoredProcedure);
This allows me to set
Variables.UserID = userinfo.UserID;
without red-squiggle lines however during run-time i get an error on the execute scalar of "System.InvalidCastException: 'Invalid cast from 'System.String' to 'Name_Space.User'.'
I have checked the User Class to ensure the data type matches with the Database and i see no problems there, I'm not sure what I'm doing wrong?
If you want value from only one column of only one row, use ExecuteScalar which is similar to ADO.NET ExecuteScalar. It will return object with which you have to deal further.
string sql = "SELECT COL1 FROM Table1 WHERE ID = 1";
//OR
//string sql = "SELECT TOP 1 COL1 FROM Table1";
//OR similar
object colValue = conn.ExecuteScalar(sql, ....);
If matching record not found, return value will be null.
Check Dapper documentation for other generic variants of method:
public static T ExecuteScalar<T>(this IDbConnection cnn, CommandDefinition command);
If you want single column from multiple rows, the way you are doing this now is correct. Just modify your SQL query/Stored Procedure to return the same. Dapper will only map returned column. All other properties in your User will remain unassigned.
If you simply want to assign values to Variables.UserID instead of binding those using DataSource, then just do that like:
Variables.UserID = userinfo.UserID;
Variables.Userfull = userinfo.UserFullName;
//and so on....
So, complete code will be something like below:
using(SqlConnection conn = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["MfgDataCollector"].ToString()))
{
DynamicParameters param = new DynamicParameters();
param.Add("#UserID", txt_userid.Text.Trim());
User userinfo = conn.Query<User>("GetUserInfo", param, commandType: CommandType.StoredProcedure).ToList<User>().First();
Variables.UserID = userinfo.UserID;
Variables.Userfull = userinfo.UserFullName;
}
Below is my code for entity and a function where I need to map entity TblEmployee from a key value pair.
In foreach loop I am getting values based on keys, what should be the best approach to do it?
public class TblEmployee
{
public int EmployeeId { get; set; }
public string Name { get; set; }
}
public int Create()
{
tblEmployee employee = new tblEmployee();
using (var ctx = new theparkeee_testEntities())
{
foreach (string key in HttpContext.Current.Request.Form.AllKeys)
{
string value = HttpContext.Current.Request.Form[key];
//how to map value from key value pair to entity employee.
}
}
}
You can use System.Reflection to get the Properties of an object by their name with Type.GetProperty(string name). After you got the PropertyInfo, you can use SetValue to assign a value to it.
foreach (string key in HttpContext.Current.Request.Form.AllKeys) {
// note that "value" is a reserved word, do not use it as variable name
string val = HttpContext.Current.Request.Form[key];
var propertyInfo = typeof(TblEmployee).GetProperty(key); // can maybe be moved outside of the loop
if (propertyInfo != null) {
propertyInfo.SetValue(employee, val);
}
}
This will work for string properties. If the property is of another type, you have to find the correct type (again, using reflection) and cast the string value before assigning it.
Note that this is not the correct approach to store data in MVC. You should not work with the Request.Form directly, instead your POST action should accept a ViewModel that can be mapped (e.g. using Automapper) to the DB entity. I.e. let the ASP ModelBinder do its work, instead of reinventing the wheel!
[HttpPost]
public ActionResult Submit(MyViewModel postData) {
var employee = Mapper.Map<TblEmployee>(postData);
_ctx.Employees.Add(employee);
_ctx.SaveChanges();
return new HttpStatusCodeResult((int)HttpStatusCode.OK);
}
I'd like to know how can I search for empty strings when I'm using a text type field with Entity Framework.
I've looked the SQL query that Entity is generating and It's using LIKE to compare because It's searching in a text type field, so when I use .Equals(""), == "", == string.Empty, .Contains(""), .Contains(string.Empty), and everything else, It's returning all results because it sql query is like '' and the == command throws exception because It uses the = command that is not valid with text type field.
When I try to use .Equals(null), .Contains(null), == null, It returns nothing, because It is generating FIELD ISNULL command.
I already tried the .Lenght == 0 but It throws an exception...
This works for me:
public class POCO
{
public int Id { get; set; }
public string Name { get; set; }
public string Description { get; set; }
}
static void Main(string[] args)
{
var pocos = new List<POCO>
{
new POCO { Id = 1, Name = "John", Description = "basic" },
new POCO { Id = 2, Name = "Jane", Description = "" },
new POCO { Id = 3, Name = "Joey", Description = string.Empty }
};
pocos.Where(x => x.Description == string.Empty)
.ToList()
.ForEach(x => Console.WriteLine($"{x.Id} {x.Name} {x.Description}"));
}
However the issue MAY BE that your T4 generated object is not fully realized with data you can use, if you are using Entity Framework. EG the translation from the database is not populating objects to interrogate correctly. I would just do an operation like this to see:
using (var context = new YOURCONTEXTNAME())
{
var persons = context.YOURDATABASEOBJECT.ToList();
persons.ForEach(x => Console.WriteLine($"{x.COLUMNINQUESTION}"));
}
If you are successfully having data in it, it should be retrieved. I would not use text if possible. Use a varchar(max) nvarchar(max) xml, whatever text will be deprecated eventually and is bad form so to speak to continue using at this point.
EDIT
Okay I see, the answer is you cannot interogate the object until it is fully realized when it is text. I did a test on my local database and created a context and tested it and sure enough you cannot do a '== string.empty', '== ""', or 'String.IsNullOrEmpty()' on a text. However you can do it once the object is materialized in a realized object. EG:
// Won't work as context does not understand type
//var persons = context.tePersons.Where(x => x.Description == string.Empty).ToList();
//Works fine as transformation got the object translated to a string in .NET
var start = context.tePersons.ToList();
var persons = start.Where(x => x.Description == String.Empty).ToList();
This poses a problem obviously as you need to get ALL your data potentially before performing a predicate. Not the best means by any measure. You could do a sql object for this instead then to do a function, proc, or view to change this.
Earlier I had a table named ApplicationConfiguration which simply had [Key],[Value] columns to store some config data. This was queried straight away using SQL queries.
Now I intend to make use of Entity Framework (EF) Code First approach to query this table. The specialty of this table is that the table will have only a fixed number of rows in its lifetime. Only the Value column can be updated.
So as per the code first approach, we have to first write our POCO classes with its properties that will be mapped to columns in the underlying table. However, I wish to have a Dictionary<> structure to represent these configuration KV pairs. My concern is, will EF be able to fire update queries against any updation to the the value of a particular pair.
Also since I am using Code First approach, I would want some seed data(i.e the fixed number of rows and its initial content) to the added after the table itself is created on the fly when the application is first executed.
If Dictionary<> cannot be used, please suggest some alternative. Thanks in advance.
Coded this way:
public class ApplicationConfiguration
{
public int Id { get; set; }
public string Key { get; set; }
public int Value { get; set; } // should be string, but I'm lazy
}
class Context : DbContext
{
internal class ContextInitializer : DropCreateDatabaseIfModelChanges<Context>
{
protected override void Seed(Context context)
{
var defaults = new List<ApplicationConfiguration>
{
new ApplicationConfiguration {Key = "Top", Value = 5},
new ApplicationConfiguration {Key = "Bottom", Value = 7},
new ApplicationConfiguration {Key = "Left", Value = 1},
new ApplicationConfiguration {Key = "Right", Value = 3}
};
// foreach (var c in defaults)
// context.ConfigurationMap.Add(c.Key, c); // by design, no IReadOnlyDictionary.Add
foreach (var c in defaults)
context.ApplicationConfigurations.Add(c);
base.Seed(context);
}
}
public Context()
{
Database.SetInitializer(new ContextInitializer());
}
private IDbSet<ApplicationConfiguration> ApplicationConfigurations
{
get { return Set<ApplicationConfiguration>(); }
}
public IReadOnlyDictionary<string, ApplicationConfiguration> ConfigurationMap
{
get { return ApplicationConfigurations.ToDictionary(kvp => kvp.Key, kvp => kvp); }
}
}
Used this way:
using (var context = new Context())
{
ReadConfigurationOnly(context.ConfigurationMap);
}
using (var context = new Context())
{
ModifyConfiguration(context.ConfigurationMap);
context.SaveChanges();
}
static void ReadConfigurationOnly(IReadOnlyDictionary<string, ApplicationConfiguration> configuration)
{
foreach (var k in configuration.Keys)
Console.WriteLine("{0} = {1}", k, configuration[k].Value);
}
static void ModifyConfiguration(IReadOnlyDictionary<string, ApplicationConfiguration> configuration)
{
foreach (var k in configuration.Keys)
configuration[k].Value++; // this is why I was lazy, using an int for a string
}
So, I wrote it up this way — using an int Value property rather than a string — just so I could run the "Used this way" code over and over, and see the database update each time, without having to come up with some other way to change Value in an interesting way.
It's not quite as nifty here to use a IReadOnlyDictionary<string, ApplicatonConfiguration> instead of a IReadOnlyDictionary<string, string>, the way we'd really like, but that's more than made up for by the fact that we can easily modify our collection values without resorting to a clumsier Set method taking a dictionary as input. The drawback, of course, is that we have to settle for configuration[key].Value = "new value" rather than configuration[key] = "new value", but — as I say — I think it's worth it.
EDIT
Dang! I wrote this code up specifically to answer this question, but I think I like it so much, I'm going to add it to my bag of tricks ... this would fit in really well when my company goes from local databases to Azure instances in the cloud, and the current app.config has to go into the database.
Now all I need is a ContextInitializer taking a System.Configuration.ConfigurationManager as a ctor parameter in order to seed a new database from an existing app.config ...
I don't think you can map a table directly to a Dictionary; you will probably have to write your own wrapper to fill a dictionary from the table and update it back to the DB. Entities are each a row of a given table... Something like this (untested):
public Dictionary<string, string> GetDictionary()
{
Dictionary<string, string> dic = new Dictionary<string, string>();
using (var db = new Context())
{
var configs = db.ApplicationConfiguration.Select();
foreach (var entry in configs)
{
dic.Add(config.Key, config.Value);
}
}
return dic;
}
public void SaveConfig(Dictionary<string, string> dic)
{
using (var db = new Context())
{
foreach (KeyValuePair kvp in dic)
{
if (!db.ApplicationConfiguration.First(a => a.Key == kvp.Key).Value == kvp.Value)
{
var ac = new ApplicationConfiguration();
ac.Key = kvp.Key;
ac.Value = kvp.Value;
db.Entry(ac).State = EntityState.Modified;
}
}
db.SaveChanges();
}
}
For your second question, you want to use the Seed() method to add initial values to the database. See here for an example implementation.
i have the following code but don't understand where am i getting wrong. There are five items in the xml file but this code shows none.
public static List<string> LoadLedgersString()
{
List<string> ListLedgerStringRecords = new List<string>();
// Execute the query using the LINQ to XML
XDocument doc = XDocument.Load(#"Ledgers.xml");
var records = from r in doc.Element("Ledgers").Elements("Ledger") select r;
foreach (var record in records)
{
string lLedgerString = record.Element("Name").Value;
ListLedgerStringRecords.Add(lLedgerString);
}
return ListLedgerStringRecords;
}
The code that is calling and utilizing its result is following
List<string> ledgerList = new List<string>();
ledgerList = DAL_Ledgers.LoadLedgersString();
ledgerListView.DataContext = ledgerList;
ICollectionView view =
CollectionViewSource.GetDefaultView(ledgerList);
new TextSearchFilter(view, this.searchTextBox);
This will probably be a problem with namespacing or with pathing.
Please post some example XML, then we can try to help.