2014年7月9日 · SELECT MyDateTimeColumn FROM MyTable WHERE CAST(MyDateTimeColumn AS DATE) = '2014-07-09' is a slower way to trim the time over DATETIME columns, I have searched but I can't find anything about this strict sentence and I don't know how to show that impresive statistics about time consuming cast/convert to probe it …

2009年10月12日 · Class#cast takes responsibility for type checking at run-time rather than during compilation. There are certainly use-cases for Class#cast, particularly when it comes to reflective operations. Since lambda's came to java I personally like using Class#cast with the collections/stream API if I'm working with abstract types, for example.

2013年8月23日 · I want to cast VARCHAR to INT, but in my table i have some value like '???' then SQL Server launch this expcetion : Conversion failed when converting the varchar value '????' to data type int. Severity 16 I could convert this '???' to NULL, that's no problem, but how do that ? I'm trying to do something like this:

When a prvalue v of type “pointer to T1” is converted to the type “pointer to cv T2”, the result is static_cast<cv T2*>(static_cast<cv void*>(v)) if both T1 and T2 are standard-layout types (3.9 [basic.types]) and the alignment requirements of T2 are no stricter than those of T1, or if …

2009年6月9日 · You can't cast using normal casting syntax if all you have is the Type object. If you want to be able to use the object as some type T at compile time, not runtime, you need to cast it using a type variable or just the actual type name. …

CStr(var) is the VB string cast operator. I'm not a VB guy, so I would suggest avoiding it, but it's not really going to hurt anything. I think it is basically the same as CType. CType(var, String) will convert the given type into a string, using any provided conversion operators. DirectCast(var, String) is used to up-cast an object into a ...

"A cast always creates a temporary of the target type (although if the target type is a reference, you won't notice)" If the target type is a reference, than the cast will not create a temporary; it will make a lvalue.

SQL Queries */ select CAST(id as CHAR(50)) as col1 from t9; select CONVERT(id, CHAR(50)) as colI1 from t9; Besides the fact that you were trying to convert to an incorrect datatype, the syntax that you were using for convert was incorrect.

2008年8月26日 · dynamic_cast only supports pointer and reference types. It returns NULL if the cast is impossible if the type is a pointer or throws an exception if the type is a reference type. Hence, dynamic_cast can be used to check if an object is of a given type, static_cast cannot (you will simply end up with an invalid value).

Here is a shortened example that avoids the "unchecked cast" warning by employing two strategies mentioned in other answers. Pass down the Class of the type of interest as a parameter at runtime (Class<T> inputElementClazz). Then you can use: inputElementClazz.cast(anyObject);