Table of Contents

Class Configuration.Linq

Namespace
LinqToDB.Common
Assembly
linq2db.dll

LINQ query settings.

public static class Configuration.Linq
Inheritance
Configuration.Linq

Properties

CacheSlidingExpiration

Specifies timeout when query will be evicted from cache since last execution of query. Default value is 1 hour.

public static TimeSpan CacheSlidingExpiration { get; set; }

Property Value

TimeSpan

CompareNullsAsValues

If set to true nullable fields would be checked for IS NULL in Equal/NotEqual comparisons. This affects: Equal, NotEqual, Not Contains Default value: true.

public static bool CompareNullsAsValues { get; set; }

Property Value

bool

Examples

public class MyEntity
{
    public int? Value;
}

db.MyEntity.Where(e => e.Value != 10)

from e1 in db.MyEntity
join e2 in db.MyEntity on e1.Value equals e2.Value
select e1

var filter = new [] {1, 2, 3};
db.MyEntity.Where(e => ! filter.Contains(e.Value))

Would be converted to next queries:

SELECT Value FROM MyEntity WHERE Value IS NULL OR Value != 10

 SELECT e1.Value
 FROM MyEntity e1
 INNER JOIN MyEntity e2 ON e1.Value = e2.Value OR (e1.Value IS NULL AND e2.Value IS NULL)

 SELECT Value FROM MyEntity WHERE Value IS NULL OR NOT Value IN (1, 2, 3)

DisableQueryCache

Used to disable LINQ expressions caching for queries. This cache reduces time, required for query parsing but have several side-effects:

- cached LINQ expressions could contain references to external objects as parameters, which could lead to memory leaks if those objects are not used anymore by other code

- cache access synchronization could lead to bigger latencies than it saves.

Default value: false.

It is not recommended to enable this option as it could lead to severe slowdown. Better approach will be to call ClearCache() method to cleanup cache after queries, that produce severe memory leaks you need to fix.

More details. 
public static bool DisableQueryCache { get; set; }

Property Value

bool

DoNotClearOrderBys

Controls behavior, when LINQ query chain contains multiple OrderBy<TSource, TKey>(IQueryable<TSource>, Expression<Func<TSource, TKey>>) or OrderByDescending<TSource, TKey>(IQueryable<TSource>, Expression<Func<TSource, TKey>>) calls:

  • if true - non-first OrderBy* call will be treated as ThenBy* call;
  • if false - OrderBy* call will discard sort specifications, added by previous OrderBy* and ThenBy* calls. Default value: false.
public static bool DoNotClearOrderBys { get; set; }

Property Value

bool

EnableContextSchemaEdit

If true, user could add new mappings to context mapping schems (MappingSchema). Otherwise LinqToDBException will be generated on locked mapping schema edit attempt. It is not recommended to enable this option as it has performance implications. Proper approach is to create single MappingSchema instance once, configure mappings for it and use this MappingSchema instance for all context instances. Default value: false.

public static bool EnableContextSchemaEdit { get; set; }

Property Value

bool

GenerateExpressionTest

Enables generation of test class for each LINQ query, executed while this option is enabled. This option could be useful for issue reporting, when you need to provide reproducible case. Test file will be placed to linq2db subfolder of temp folder and exact file path will be logged to data connection tracing infrastructure. See TraceSwitch for more details. Default value: false.

public static bool GenerateExpressionTest { get; set; }

Property Value

bool

GuardGrouping

Controls behavior of LINQ query, which ends with GroupBy call.

public static bool GuardGrouping { get; set; }

Property Value

bool

Remarks

More details.

IgnoreEmptyUpdate

Controls behavior of linq2db when there is no updateable fields in Update query:

  • if true - query not executed and Update operation returns 0 as number of affected records;
  • if false - LinqException will be thrown. Default value: false.
public static bool IgnoreEmptyUpdate { get; set; }

Property Value

bool

KeepDistinctOrdered

Allows SQL generation to automatically transform

SELECT DISTINCT value FROM Table ORDER BY date

Into GROUP BY equivalent if syntax is not supported Default value: true.

public static bool KeepDistinctOrdered { get; set; }

Property Value

bool

OptimizeJoins

If enabled, linq2db will try to reduce number of generated SQL JOINs for LINQ query. Attempted optimizations:

  • removes duplicate joins by unique target table key;
  • removes self-joins by unique key;
  • removes left joins if joined table is not used in query. Default value: true.
public static bool OptimizeJoins { get; set; }

Property Value

bool

Options

Default LinqOptions options. Automatically synchronized with other settings in Configuration.Linq class.

public static LinqOptions Options { get; set; }

Property Value

LinqOptions

ParameterizeTakeSkip

Enables Take/Skip parameterization. Default value: true.

public static bool ParameterizeTakeSkip { get; set; }

Property Value

bool

PreferApply

Used to generate CROSS APPLY or OUTER APPLY if possible. Default value: true.

public static bool PreferApply { get; set; }

Property Value

bool

PreloadGroups

Controls how group data for LINQ queries ended with GroupBy will be loaded:

  • if true - group data will be loaded together with main query, resulting in 1 + N queries, where N - number of groups;
  • if false - group data will be loaded when you call enumerator for specific group IGrouping<TKey, TElement>. Default value: false.
public static bool PreloadGroups { get; set; }

Property Value

bool

TraceMapperExpression

Enables logging of generated mapping expression to data connection tracing infrastructure. See TraceSwitch for more details. Default value: false.

public static bool TraceMapperExpression { get; set; }

Property Value

bool