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 ?
In order to get multiple result sets working we need to drop to the ObjectContext API by using the IObjectContextAdapter interface. Once we have an ObjectContext then we can use the Translate method to translate the results of our stored procedure into entities that can be tracked and used in EF as normal.
Most stored procedures return multiple result sets. Such a stored procedure usually includes one or more select statements. The consumer needs to consider this inclusion to handle all the result sets.
Multiple Active Result Sets (MARS) is a feature that allows the execution of multiple batches on a single connection. In previous versions, only one batch could be executed at a time against a single connection. Executing multiple batches with MARS does not imply simultaneous execution of operations.
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
In the interim there is an excellent solution being posted on the GitHub issue for any one looking for an alternative 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]);
}
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