HasQueryFilter
的非泛型EntityTypeBuilder
(与泛型相反EntityTypeBuilder<TEntity>
)几乎无法使用,因为没有简单的方法来创建预期的LambdaExpression
.
一种解决方案是使用Expression
类方法手动构建 lambda 表达式:
.ForEach(entityType =>
{
builder.Entity(entityType.ClrType).Property<Boolean>("IsDeleted");
var parameter = Expression.Parameter(entityType.ClrType, "e");
var body = Expression.Equal(
Expression.Call(typeof(EF), nameof(EF.Property), new[] { typeof(bool) }, parameter, Expression.Constant("IsDeleted")),
Expression.Constant(false));
builder.Entity(entityType.ClrType).HasQueryFilter(Expression.Lambda(body, parameter));
});
另一种是使用原型表达式
Expression<Func<object, bool>> filter =
e => EF.Property<bool>(e, "IsDeleted") == false;
并使用参数替换器将参数与实际类型绑定:
.ForEach(entityType =>
{
builder.Entity(entityType.ClrType).Property<Boolean>("IsDeleted");
var parameter = Expression.Parameter(entityType.ClrType, "e");
var body = filter.Body.ReplaceParameter(filter.Parameters[0], parameter);
builder.Entity(entityType.ClrType).HasQueryFilter(Expression.Lambda(body, parameter));
});
哪里ReplaceParameter
是我用于表达式树操作的自定义助手扩展方法之一:
public static partial class ExpressionUtils
{
public static Expression ReplaceParameter(this Expression expr, ParameterExpression source, Expression target) =>
new ParameterReplacer { Source = source, Target = target }.Visit(expr);
class ParameterReplacer : System.Linq.Expressions.ExpressionVisitor
{
public ParameterExpression Source;
public Expression Target;
protected override Expression VisitParameter(ParameterExpression node) => node == Source ? Target : node;
}
}
但我认为最自然的解决方案是将配置代码移动到通用方法中并通过反射调用它。例如:
static void ConfigureSoftDelete<T>(ModelBuilder builder)
where T : class, IDeletableEntity
{
builder.Entity<T>().Property<Boolean>("IsDeleted");
builder.Entity<T>().HasQueryFilter(e => EF.Property<bool>(e, "IsDeleted") == false);
}
接着
.ForEach(entityType => GetType()
.GetMethod(nameof(ConfigureSoftDelete), BindingFlags.NonPublic | BindingFlags.Static)
.MakeGenericMethod(entityType.ClrType)
.Invoke(null, new object[] { builder })
);