public void EmptyTest()
{
Emptyable.Register(typeof(IEmptyA <>), typeof(EmptyB <>)); //? 接口注册。
Emptyable.Register(typeof(EmptyA <>), typeof(EmptyC <>)); //? 抽象类注册。
var i = Emptyable.Empty <int>();
var e = Emptyable.Empty <DateTimeKind>();
var d = Emptyable.Empty <DateTime>();
var s = Emptyable.Empty <string>();
var c = Emptyable.Empty <CopyTest>(); //? 默认构造函数。
var nc = Emptyable.Empty <NonPublicConstructor>(); //? 私有构造函数。
var na = Emptyable.Empty <HasArgumentsConstructor>(); //? 有参数构造函数。
var ng = Emptyable.Empty <IEmptyA <int> >();
var ng2 = Emptyable.Empty <EmptyA <string> >();
}
/// <inheritdoc />
protected override void StartupCore(MethodCallExpression node)
{
switch (node.Method.Name)
{
case MethodCall.Count when node.Arguments.Count == 2:
case MethodCall.LongCount when node.Arguments.Count == 2:
writer.Write("COUNT");
writer.OpenBrace();
writer.Write("CASE WHEN ");
VisitCondition(node);
writer.Write(" THEN 1 ELSE 0 END");
writer.CloseBrace();
break;
case MethodCall.Count when node.Arguments[0].NodeType == ExpressionType.Parameter:
case MethodCall.LongCount when node.Arguments[0].NodeType == ExpressionType.Parameter:
writer.Write("COUNT(1)");
break;
case MethodCall.Count:
case MethodCall.LongCount:
writer.Write("COUNT");
writer.OpenBrace();
writer.Write("CASE WHEN ");
Visit(node.Arguments[0]);
writer.Write(" THEN 1 ELSE 0 END");
writer.CloseBrace();
break;
case MethodCall.Sum when node.Arguments.Count == 2 && node.Arguments[0].NodeType == ExpressionType.Parameter:
case MethodCall.Max when node.Arguments.Count == 2 && node.Arguments[0].NodeType == ExpressionType.Parameter:
case MethodCall.Min when node.Arguments.Count == 2 && node.Arguments[0].NodeType == ExpressionType.Parameter:
case MethodCall.Average when node.Arguments.Count == 2 && node.Arguments[0].NodeType == ExpressionType.Parameter:
writer.Write(node.Method.Name == MethodCall.Average ? "AVG" : node.Method.Name.ToUpper());
writer.OpenBrace();
Visit(node.Arguments[1]);
writer.CloseBrace();
break;
case MethodCall.Sum when node.Arguments.Count == 2:
case MethodCall.Max when node.Arguments.Count == 2:
case MethodCall.Min when node.Arguments.Count == 2:
case MethodCall.Average when node.Arguments.Count == 2:
writer.Write(node.Method.Name == MethodCall.Average ? "AVG" : node.Method.Name.ToUpper());
writer.OpenBrace();
writer.Write("CASE WHEN ");
Visit(node.Arguments[0]);
writer.Write(" THEN ");
Visit(node.Arguments[1]);
writer.Write(" ELSE ");
var returnType = node.Method.ReturnType;
if (!returnType.IsValueType || returnType.IsNullable())
{
writer.Null();
}
else if (returnType == Types.DateTime)
{
writer.Parameter("date_utc_base", UtcBase);
}
else if (returnType == Types.DateTimeOffset)
{
writer.Parameter("date_offset_utc_base", new DateTimeOffset(UtcBase));
}
else
{
writer.Parameter($"{returnType.Name.ToUrlCase()}_default", Emptyable.Empty(node.Method.ReturnType));
}
writer.Write(" END");
writer.CloseBrace();
break;
case MethodCall.Any when node.Arguments.Count == 1 && node.Arguments[0].NodeType == ExpressionType.Parameter:
writer.BooleanTrue();
break;
case MethodCall.Any when node.Arguments.Count == 1:
writer.Write("CASE ");
writer.Write("MAX");
writer.OpenBrace();
writer.Write("CASE WHEN ");
Visit(node.Arguments[0]);
writer.Write(" THEN 1 ELSE 0 END");
writer.CloseBrace();
writer.Write(" WHEN 1 THEN ");
writer.BooleanTrue();
writer.Write(" ELSE ");
writer.BooleanFalse();
writer.Write(" END");
break;
case MethodCall.Any when node.Arguments.Count == 2:
case MethodCall.All when node.Arguments.Count == 2:
writer.Write("CASE ");
writer.Write(node.Method.Name == MethodCall.Any ? "MAX" : "MIN");
writer.OpenBrace();
writer.Write("CASE WHEN ");
VisitCondition(node);
writer.Write(" THEN 1 ELSE 0 END");
writer.CloseBrace();
writer.Write(" WHEN 1 THEN ");
writer.BooleanTrue();
writer.Write(" ELSE ");
writer.BooleanFalse();
writer.Write(" END");
break;
case MethodCall.Sum:
case MethodCall.Max:
case MethodCall.Min:
case MethodCall.Average:
throw new DSyntaxErrorException($"分组中函数“{node.Method.Name}”需指定计算属性!");
default:
throw new DSyntaxErrorException($"分组中函数“{node.Method.Name}”不被支持!");
}
}