protected override Expression VisitMethodCall(MethodCallExpression methodCallExpression)
{
if (methodCallExpression.Object == null &&
methodCallExpression.Method.DeclaringType == typeof(Enumerable) &&
methodCallExpression.Arguments.Count == 2 &&
methodCallExpression.Arguments[0] is GroupByShaperExpression groupByShaperExpression &&
methodCallExpression.Method.Name == nameof(Enumerable.Count))
{
var selectorLambda = (LambdaExpression)methodCallExpression.Arguments[1];
if (selectorLambda.Body is SelectDistinctExpression selectDistinct)
{
Expression selector = ReplacingExpressionVisitor.Replace(selectDistinct.Selector.Parameters[0],
groupByShaperExpression.ElementSelector, selectDistinct.Selector.Body);
selector = base.Visit(selector);
SqlFragmentExpression distinctFragment = base.Dependencies.SqlExpressionFactory.Fragment("DISTINCT ");
RelationalTypeMapping boolTypeMapping = base.Dependencies.SqlExpressionFactory.FindMapping(typeof(bool));
var selectDistinctSql = new SelectDistinctSqlExpression(selector, distinctFragment, boolTypeMapping);
return(base.Dependencies.SqlExpressionFactory.Function("COUNT", new[] { selectDistinctSql }, typeof(int)));
}
}
return(base.VisitMethodCall(methodCallExpression));
}
private bool Equals(SelectDistinctSqlExpression distinctCountExpression)
{
return(base.Equals(distinctCountExpression) && Selector.Equals(distinctCountExpression.Selector));
}
