protected virtual string GetOperator(UnaryExpression u)
{
switch (u.NodeType)
{
case SqlExpressionType.Exists:
return "EXISTS";
case SqlExpressionType.IsNull:
return "IS NULL";
case SqlExpressionType.Negate:
return "-";
case SqlExpressionType.Not:
return "NOT";
case SqlExpressionType.UnaryPlus:
return "+";
default:
throw new NotSupportedException("不支持的操作符：" + u.NodeType);
}
}
protected override SqlExpression VisitUnary(UnaryExpression expr)
{
if (expr.NodeType == SqlExpressionType.IsNull)
{
this.Write("(");
this.Visit(expr.Operand);
this.Write(") ");
this.Write(GetOperator(expr));
}
else
{
this.Write(GetOperator(expr));
this.Write(" (");
this.Visit(expr.Operand);
this.Write(") ");
}
return expr;
}
