Develop Reference

Problems with linq in getting data from list

I have problem
I need to get list from list in linq. But it type of list is unknown on compilation stage.
using(var context = MyDbContext())
{
var list = (from p in context.Employee select p).ToList()
}
I dont know what just property (change Employee)
I want to do something that
public IList<T> GetAll(string propName)
{
using (var context = new ModelContext())
{
return (from p in context.GetType().GetProperty(propName) select p).ToList();
}
}

The DbContext.Database property provides an API that allows you to perform ADO.NET operations directly. The GetDbConnection method returns a DbConnection object representing the context's underlying connection. From that point, you can revert to the familiar ADO.NET APIs:
public dynamic GetAll(string propName)
{
using (var context = new SampleContext())
using (var command = context.Database.GetDbConnection().CreateCommand())
{
//Escape propName to prevent SQL injection
var builder = new SqlCommandBuilder();
string escapedTableName = builder.QuoteIdentifier(propName);
command.CommandText = $"SELECT * From {escapedTableName}";
context.Database.OpenConnection();
using (var dataReader= command.ExecuteReader())
{
var dataTable = new DataTable();
dataTable.Load(dataReader);
return dataTable ;
}
}
}

Dynamic SQLite Query db.Table<DYNAMIC> C#/UWP

I should a DB Handler class develop. I want a method like dynamic Select, Update, Delete...
This is my code;
using (var db = new SQLiteConnection(this.dbPath))
{
lst = db.Table<tabCOProzessRow>()).ToList();
}
But I wanna like this; (with where condition)
using (var db = new SQLiteConnection(this.dbPath))
{
lst = db.Table<***DYNAMIC***>()).ToList();
}
Is it possible?
Thank you...

I could make a dynamic query with this code;
public List<object> getTable(string TableName)
{
object[] obj = new object[] { };
TableMapping map = new TableMapping(Type.GetType(TableName));
string query = "select * from " + TableName;
return db.Query(map, "query", obj).ToList();
}
We can be more dynamically with buildQuery method.

Working with multiple resultset in .net core

While retrieving the results using stored procedure how can I retrieve and store multiple result set in view model in .net core
For e.g. from stored procedure I am returning records for below two queries
Select * LMS_Survey
Select * from LMS_SurveyQuestion
Select * from LMS_SurveyQuestionOptionChoice
and below is view model for two tables
public class LMS_SurveyTraineeViewModel
{
public LMS_SurveyDetailsViewModel SurveyDetailsViewModel { get; set; }
public LMS_SurveyQuestionsViewModel SurveyQuestionsViewModel { get; set; }
public LMS_SurveyQuestionOptionChoiceViewModel SurveyQuestionOptionChoiceViewModel { get; set; }
}
This is how I am executing the stored procedure
public List<LMS_SurveyTraineeViewModel> GetTraineeSurvey(int surveyID)
{
try
{
List<LMS_SurveyTraineeViewModel> modelList = new List<LMS_SurveyTraineeViewModel>();
modelList = dbcontext.Set<LMS_SurveyTraineeViewModel>().FromSql("LMSSP_GetTraineeSurvey #surveyID = {0},#LanguageID = {1}", surveyID, AppTenant.SelectedLanguageID).ToList();
return modelList;
}
catch (Exception ex)
{
throw ex;
}
}
How can stored the multiple result set using stored procedure in view model ?

Currently, EF Core doesn't not support this. There is an open issue to address this.
https://github.com/aspnet/EntityFramework/issues/8127
Update 12th Sep 2018: This is still not a priority for EF Core even for release 3.0; so best use Dapper or plain ADO.NET when you have multiple results scenario
Update 25th Jun 2020: still on the backlog for EF Core even for release 5.0; so best use Dapper or plain ADO.NET when you have multiple results scenario
Update 7th Feb 2021: still on the backlog for EF Core
Update 8th Aug 2022: still on the backlog for EF Core, looks like its not a high priority use-case. Recommend to follow alternatives like using straight ADO.NET or Dapr or the below workaround for this
In the interim an alternative solution can be achieved via extension method(s)
public static async Task<IList<IList>> MultiResultSetsFromSql(this DbContext dbContext, ICollection<Type> resultSetMappingTypes, string sql, params object[] parameters)
{
var resultSets = new List<IList>();
var connection = dbContext.Database.GetDbConnection();
var parameterGenerator = dbContext.GetService<IParameterNameGeneratorFactory>()
.Create();
var commandBuilder = dbContext.GetService<IRelationalCommandBuilderFactory>()
.Create();
foreach (var parameter in parameters)
{
var generatedName = parameterGenerator.GenerateNext();
if (parameter is DbParameter dbParameter)
commandBuilder.AddRawParameter(generatedName, dbParameter);
else
commandBuilder.AddParameter(generatedName, generatedName);
}
using var command = connection.CreateCommand();
command.CommandType = CommandType.Text;
command.CommandText = sql;
command.Connection = connection;
for (var i = 0; i < commandBuilder.Parameters.Count; i++)
{
var relationalParameter = commandBuilder.Parameters[i];
relationalParameter.AddDbParameter(command, parameters[i]);
}
var materializerSource = dbContext.GetService<IEntityMaterializerSource>();
if (connection.State == ConnectionState.Closed)
await connection.OpenAsync();
using var reader = await command.ExecuteReaderAsync();
foreach (var pair in resultSetMappingTypes.Select((x, i) => (Index: i, Type: x)))
{
var i = pair.Index;
var resultSetMappingType = pair.Type;
if (i > 0 && !(await reader.NextResultAsync()))
throw new InvalidOperationException(string.Format("No result set at index {0}, unable to map to {1}.", i, resultSetMappingType));
var type = resultSetMappingType;
var entityType = dbContext.GetService<IModel>()
.FindEntityType(type);
if (entityType == null)
throw new InvalidOperationException(string.Format("Unable to find a an entity type (or query type) matching '{0}'", type));
var relationalTypeMappingSource = dbContext.GetService<IRelationalTypeMappingSource>();
var columns = Enumerable.Range(0, reader.FieldCount)
.Select(x => new
{
Index = x,
Name = reader.GetName(x)
})
.ToList();
var relationalValueBufferFactoryFactory = dbContext.GetService<IRelationalValueBufferFactoryFactory>();
int discriminatorIdx = -1;
var discriminatorProperty = entityType.GetDiscriminatorProperty();
var entityTypes = entityType.GetDerivedTypesInclusive();
var instanceTypeMapping = entityTypes.Select(et => new
{
EntityType = et,
Properties = et.GetProperties()
.Select(x =>
{
var column = columns.FirstOrDefault(y => string.Equals(y.Name,
x.GetColumnName() ?? x.Name, StringComparison.OrdinalIgnoreCase)) ?? throw new InvalidOperationException(string.Format("Unable to find a column mapping property '{0}'.", x.Name));
if (x == discriminatorProperty)
discriminatorIdx = column.Index;
return new TypeMaterializationInfo(x.PropertyInfo.PropertyType, x, relationalTypeMappingSource, column.Index);
})
.ToArray()
})
.Select(x => new
{
EntityType = x.EntityType,
Properties = x.Properties,
ValueBufferFactory = relationalValueBufferFactoryFactory.Create(x.Properties)
})
.ToDictionary(e => e.EntityType.GetDiscriminatorValue() ?? e.EntityType, e => e)
;
var resultSetValues = (IList)Activator.CreateInstance(typeof(List<>).MakeGenericType(type));
while (await reader.ReadAsync())
{
var instanceInfo = discriminatorIdx < 0 ? instanceTypeMapping[entityType] : instanceTypeMapping[reader[discriminatorIdx]];
var valueBuffer = instanceInfo.ValueBufferFactory.Create(reader);
var materializationAction = materializerSource.GetMaterializer(instanceInfo.EntityType);
resultSetValues.Add(materializationAction(new MaterializationContext(valueBuffer, dbContext)));
}
resultSets.Add(resultSetValues);
}
return resultSets;
}
And the extension typed methods
public static async Task<(IReadOnlyCollection<T1> FirstResultSet, IReadOnlyCollection<T2> SecondResultSet)> MultiResultSetsFromSql<T1, T2>(this DbContext dbContext, string sql, params object[] parameters)
{
var resultSetMappingTypes = new[]
{
typeof(T1), typeof(T2)
};
var resultSets = await MultiResultSetsFromSql(dbContext, resultSetMappingTypes, sql, parameters);
return ((IReadOnlyCollection<T1>)resultSets[0], (IReadOnlyCollection<T2>)resultSets[1]);
}
public static async Task<(IReadOnlyCollection<T1> FirstResultSet, IReadOnlyCollection<T2> SecondResultSet, IReadOnlyCollection<T3> ThirdResultSet)> MultiResultSetsFromSql<T1, T2, T3>(this DbContext dbContext, string sql, params object[] parameters)
{
var resultSetMappingTypes = new[]
{
typeof(T1), typeof(T2), typeof(T3)
};
var resultSets = await MultiResultSetsFromSql(dbContext, resultSetMappingTypes, sql, parameters);
return ((IReadOnlyCollection<T1>)resultSets[0], (IReadOnlyCollection<T2>)resultSets[1], (IReadOnlyCollection<T3>)resultSets[2]);
}

Currently, EF Core doesn't not support this. see this example for retrieve multiple result sets.
https://github.com/nilendrat/EfCoreMultipleResults/

It works with this tiny change on EF core 5 according to Ricky G answer
change
command.CommandType = CommandType.Text;
to
command.CommandType = CommandType.StoredProcedure;
and as sql parameter value for this extension method type your stored procedure name "dbo.testproc"
example of usage:
var t1 = await _context.MultiResultSetsFromSql(new [] {typeof(proctestprocResult) },"dbo.testproc", sqlParameters);
works for me

DataAdapter .Update does not update back table

my problem is very common, but I have not found any solution.
This is my code:
public async Task<QueryResult> RollbackQuery(ActionLog action)
{
var inputParameters = JsonConvert.DeserializeObject<Parameter[]>(action.Values);
var data = DeserailizeByteArrayToDataSet(action.RollBackData);
using (var structure = PrepareStructure(action.Query, action.Query.DataBase, inputParameters))
{
//_queryPlanner is the implementor for my interface
return await _queryPlanner.RollbackQuery(structure, data);
}
}
I need to load DataTable (from whereever) and replace data to database. This is my Rollback function. This function use a "CommandStructure" where I've incapsulated all SqlClient objects. PrepareStructure initialize all objects
//_dataLayer is an Helper for create System.Data.SqlClient objects
//ex: _dataLayer.CreateCommand(preSelect) => new SqlCommand(preSelect)
private CommandStructure PrepareStructure(string sql, string preSelect, DataBase db, IEnumerable<Parameter> inputParameters)
{
var parameters = inputParameters as IList<Parameter> ?? inputParameters.ToList();
var structure = new CommandStructure(_logger);
structure.Connection = _dataLayer.ConnectToDatabase(db);
structure.SqlCommand = _dataLayer.CreateCommand(sql);
structure.PreSelectCommand = _dataLayer.CreateCommand(preSelect);
structure.QueryParameters = _dataLayer.CreateParemeters(parameters);
structure.WhereParameters = _dataLayer.CreateParemeters(parameters.Where(p => p.IsWhereClause.HasValue && p.IsWhereClause.Value));
structure.CommandBuilder = _dataLayer.CreateCommandBuilder();
structure.DataAdapter = new SqlDataAdapter();
return structure;
}
So, my function uses SqlCommandBuilder and DataAdapter to operate on Database.
PreSelectCommand is like "Select * from Purchase where CustomerId = #id"
The table Purchase has one primaryKey on ID filed
public virtual async Task<QueryResult> RollbackQuery(CommandStructure cmd, DataTable oldData)
{
await cmd.OpenConnectionAsync();
int record = 0;
using (var cmdPre = cmd.PreSelectCommand as SqlCommand)
using (var dataAdapt = new SqlDataAdapter(cmdPre))
using (var cmdBuilder = new SqlCommandBuilder(dataAdapt))
{
dataAdapt.UpdateCommand = cmdBuilder.GetUpdateCommand();
dataAdapt.DeleteCommand = cmdBuilder.GetDeleteCommand();
dataAdapt.InsertCommand = cmdBuilder.GetInsertCommand();
using (var tbl = new DataTable(oldData.TableName))
{
dataAdapt.Fill(tbl);
dataAdapt.FillSchema(tbl, SchemaType.Source);
tbl.Merge(oldData);
foreach (DataRow row in tbl.Rows)
{
row.SetModified();
}
record = dataAdapt.Update(tbl);
}
}
return new QueryResult
{
RecordAffected = record
};
}
I Execute the code and I don't have any errors, but the data are not updated.
variable "record" contain the right number of modified (??) record, but..... on the table nothing
can someone help me?
EDIT 1:
With SQL Profiler I saw that no query is executed on DB. Only select query on .Fill(tbl) command.
EDIT 2:
Now I have made one change:
tbl.Merge(oldData) => tbl.Merge(oldData, true)
so I see perform the expected query but, with reversed parameters.
UPDATE Purchase SET price=123 where id=6 and price=22
instead of
UPDATE Purchase SET price=22 where id=6 and price=123

Using Dapper.TVP TableValueParameter with other parameters

I have a procedure that takes in a table-valued parameter, along with others:
CREATE PROCEDURE [dbo].[Update_Records]
#currentYear INT,
#country INT,
#records Record_Table_Type READONLY
AS
and am trying to call this with Dapper.TVP.
Here is the code I have so far:
var recordsParameter = new List<SqlDataRecord>();
// This metadata matches 'Record_Table_Type' in the Database
var recordsMetaData = new[]
{
new SqlMetaData("OriginalValue", SqlDbType.Decimal, 19, 4),
new SqlMetaData("NewValue", SqlDbType.Decimal, 19, 4),
new SqlMetaData("NewPercent", SqlDbType.Decimal, 7, 2),
};
foreach (var r in records)
{
var record = new SqlDataRecord(recordsMetaData);
record.SetDecimal(0, r.OriginalValue);
record.SetDecimal(1, r.NewValue);
record.SetDecimal(2, r.NewPercent);
recordsParameter.Add(record);
}
var spParams = new DynamicParameters(new
{
currentYear = filter.currentYear,
country = filter.country,
});
var recordsParam = new TableValueParameter("#records", "Record_Table_Type", recordsParameter);
using (var connection = ConnectionFactory.GetConnection())
{
connection.Execute("Update_Records", ???, commandType: CommandType.StoredProcedure);
}
My issue is how do I pass both sets of parameters to the procedure in the call to Dapper Execute()?
I have tried:
var spParams = new DynamicParameters(new
{
currentYear = filter.currentYear,
country = filter.country,
records = new TableValueParameter("#records", "Record_Table_Type", recordsParameter);
});
connection.Execute("Update_Records", spParams, commandType: CommandType.StoredProcedure);
and
connection.Execute("Update_Records", new Object[] { spParams, recordsParam }, commandType: CommandType.StoredProcedure);
Both call the procedure, but pass an empty table parameter ( SELECT COUNT(*) FROM #records returns 0 )
I can't seem to find any actual documentation or source for Dapper.TVP, so the whole thing is very confusing, and the 2nd parameter to .Execute() is just a dynamic so that again doesn't tell me what I can and can't pass to it.
Any ideas?

I am on mobile and may be misunderstanding the question, but this should be just:
DataTable records = ...
connection.Execute("Update_Records",
new {
currentYear = filter.currentYear,
country = filter.country,
records
},
commandType: CommandType.StoredProcedure
);

Based on an answer from Mark Gravell here: Does Dapper support SQL 2008 Table-Valued Parameters?
I changed my code to no longer use Dapper.TVP and instead just use a DataTable so the code is now:
var recordsTable = new DataTable();
recordsTable.Columns.Add("NewValue", typeof(Decimal));
foreach (var netRevenue in records)
{
var row = recordsTable.NewRow();
row[0] = netRevenue.NewValue;
recordsTable.Rows.Add(row);
}
recordsTable.EndLoadData();
var spParams = new DynamicParameters(new
{
currentYear = filter.currentYear,
country = filter.country,
records = recordsTable.AsTableValuedParameter("Record_Table_Type")
});
using (var connection = ConnectionFactory.GetConnection())
{
connection.Execute("Update_Records", spParams, commandType: CommandType.StoredProcedure);
}
And this works.