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Example of applying an EF Core global query filter on all entity types that implement an interface
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| using System; | |
| using System.Collections.ObjectModel; | |
| using System.Linq; | |
| using System.Linq.Expressions; | |
| using System.Reflection; | |
| using Microsoft.EntityFrameworkCore; | |
| using Microsoft.EntityFrameworkCore.Metadata.Builders; | |
| using Microsoft.EntityFrameworkCore.Metadata.Internal; | |
| using Remotion.Linq.Parsing.ExpressionVisitors; | |
| public static class ModelBuilderExtensions | |
| { | |
| static readonly MethodInfo SetQueryFilterMethod = typeof(ModelBuilderExtensions) | |
| .GetMethods(BindingFlags.NonPublic | BindingFlags.Static) | |
| .Single(t => t.IsGenericMethod && t.Name == nameof(SetQueryFilter)); | |
| public static void SetQueryFilterOnAllEntities<TEntityInterface>( | |
| this ModelBuilder builder, | |
| Expression<Func<TEntityInterface, bool>> filterExpression) | |
| { | |
| foreach (var type in builder.Model.GetEntityTypes() | |
| .Where(t => t.BaseType == null) | |
| .Select(t => t.ClrType) | |
| .Where(t => typeof(TEntityInterface).IsAssignableFrom(t))) | |
| { | |
| builder.SetEntityQueryFilter<TEntityInterface>( | |
| type, | |
| filterExpression); | |
| } | |
| } | |
| static void SetEntityQueryFilter<TEntityInterface>( | |
| this ModelBuilder builder, | |
| Type entityType, | |
| Expression<Func<TEntityInterface, bool>> filterExpression) | |
| { | |
| SetQueryFilterMethod | |
| .MakeGenericMethod(entityType, typeof(TEntityInterface)) | |
| .Invoke(null, new object[] { builder, filterExpression }); | |
| } | |
| static void SetQueryFilter<TEntity, TEntityInterface>( | |
| this ModelBuilder builder, | |
| Expression<Func<TEntityInterface, bool>> filterExpression) | |
| where TEntityInterface : class | |
| where TEntity : class, TEntityInterface | |
| { | |
| var concreteExpression = filterExpression | |
| .Convert<TEntityInterface, TEntity>(); | |
| builder.Entity<TEntity>() | |
| .AddQueryFilter(concreteExpression); | |
| } | |
| static void AddQueryFilter<T>(this EntityTypeBuilder entityTypeBuilder, Expression<Func<T, bool>> expression) | |
| { | |
| var parameterType = Expression.Parameter(entityTypeBuilder.Metadata.ClrType); | |
| var expressionFilter = ReplacingExpressionVisitor.Replace( | |
| expression.Parameters.Single(), parameterType, expression.Body); | |
| var internalEntityTypeBuilder = entityTypeBuilder.GetInternalEntityTypeBuilder(); | |
| if (internalEntityTypeBuilder.Metadata.QueryFilter != null) | |
| { | |
| var currentQueryFilter = internalEntityTypeBuilder.Metadata.QueryFilter; | |
| var currentExpressionFilter = ReplacingExpressionVisitor.Replace( | |
| currentQueryFilter.Parameters.Single(), parameterType, currentQueryFilter.Body); | |
| expressionFilter = Expression.AndAlso(currentExpressionFilter, expressionFilter); | |
| } | |
| var lambdaExpression = Expression.Lambda(expressionFilter, parameterType); | |
| entityTypeBuilder.HasQueryFilter(lambdaExpression); | |
| } | |
| static InternalEntityTypeBuilder GetInternalEntityTypeBuilder(this EntityTypeBuilder entityTypeBuilder) | |
| { | |
| var internalEntityTypeBuilder = typeof(EntityTypeBuilder) | |
| .GetProperty("Builder", BindingFlags.NonPublic | BindingFlags.Instance)? | |
| .GetValue(entityTypeBuilder) as InternalEntityTypeBuilder; | |
| return internalEntityTypeBuilder; | |
| } | |
| } | |
| public static class ExpressionExtensions | |
| { | |
| // This magic is courtesy of this StackOverflow post. | |
| // https://stackoverflow.com/questions/38316519/replace-parameter-type-in-lambda-expression | |
| // I made some tweaks to adapt it to our needs - @haacked | |
| public static Expression<Func<TTarget, bool>> Convert<TSource, TTarget>( | |
| this Expression<Func<TSource, bool>> root) | |
| { | |
| var visitor = new ParameterTypeVisitor<TSource, TTarget>(); | |
| return (Expression<Func<TTarget, bool>>)visitor.Visit(root); | |
| } | |
| class ParameterTypeVisitor<TSource, TTarget> : ExpressionVisitor | |
| { | |
| private ReadOnlyCollection<ParameterExpression> _parameters; | |
| protected override Expression VisitParameter(ParameterExpression node) | |
| { | |
| return _parameters?.FirstOrDefault(p => p.Name == node.Name) | |
| ?? (node.Type == typeof(TSource) ? Expression.Parameter(typeof(TTarget), node.Name) : node); | |
| } | |
| protected override Expression VisitLambda<T>(Expression<T> node) | |
| { | |
| _parameters = VisitAndConvert(node.Parameters, "VisitLambda"); | |
| return Expression.Lambda(Visit(node.Body), _parameters); | |
| } | |
| } | |
| } |
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