public List <QueryPropertyDescription> Provide(QueryBaseModel model)
{
return(model.GetType().GetProperties()
.Where(s => s.GetCustomAttribute <QueryPropertyAttribute>() != null)
.Select(s => new QueryPropertyDescription(s))
.ToList());
}
public Expression <Func <TEntity, bool> > Create(QueryBaseModel model)
{
var param = this.CreateParameter();
Expression body = model.CreateExpressionBody(param);
var properties = _queryPropertyProvider.Provide(model);
foreach (var property in properties)
{
var value = property.Property.GetValue(model);
if (!property.Query.AllowDefault)
{
if (property.Property.PropertyType.IsValueType)
{
var defaultValue = Activator.CreateInstance(property.Property.PropertyType);
if (value.Equals(defaultValue))//务必用equals比较，==是不对的
{
continue;
}
}
else
{
if (value == null)
{
continue;
}
}
}
var expression = property.Query.CreateExpression(param, value);
if (body == null)
{
body = expression;
}
else
{
body = Expression.AndAlso(body, expression);
}
}
;
Expression <Func <TEntity, bool> > filter = body == null ? s => true : Expression.Lambda <Func <TEntity, bool> >(body, param);
return(filter);
}
