Question

检查某个Type是否可为空的最佳方法是什么。

一些建议的代码无法测试其他Type特别是字符串。

Answer 1

<?php
if (file_exists("../../../../wp-load.php")) {
    require_once("../../../../wp-load.php");
}
$q = $_GET['k'];

global $dbhandle;//Database connection

if(isset($_GET['f'])&&$_GET['f']=='product'){
    $result = mysql_query("SELECT * from `Invoice` WHERE ProductID= ".$k);
}
$list_Client = array();
while($row=mysql_fetch_object($result)){
    $list_Client[] = $row;
}
// Load data from db and show it in div id = content
?>

Answer 2

最简单的方法：

    public static bool IsNullable(this Type type)
    {
        if (type.IsValueType) return Activator.CreateInstance(type) == null;
        return true;
    }

这些是我的单元测试，全部通过

    IsNullable_String_ShouldReturn_True
    IsNullable_Boolean_ShouldReturn_False
    IsNullable_Enum_ShouldReturn_Fasle
    IsNullable_Nullable_ShouldReturn_True
    IsNullable_Class_ShouldReturn_True
    IsNullable_Decimal_ShouldReturn_False
    IsNullable_Byte_ShouldReturn_False
    IsNullable_KeyValuePair_ShouldReturn_False

实际单元测试

    [TestMethod]
    public void IsNullable_String_ShouldReturn_True()
    {
        var typ = typeof(string);
        var result = typ.IsNullable();
        Assert.IsTrue(result);
    }

    [TestMethod]
    public void IsNullable_Boolean_ShouldReturn_False()
    {
        var typ = typeof(bool);
        var result = typ.IsNullable();
        Assert.IsFalse(result);
    }

    [TestMethod]
    public void IsNullable_Enum_ShouldReturn_Fasle()
    {
        var typ = typeof(System.GenericUriParserOptions);
        var result = typ.IsNullable();
        Assert.IsFalse(result);
    }

    [TestMethod]
    public void IsNullable_Nullable_ShouldReturn_True()
    {
        var typ = typeof(Nullable<bool>);
        var result = typ.IsNullable();
        Assert.IsTrue(result);
    }

    [TestMethod]
    public void IsNullable_Class_ShouldReturn_True()
    {
        var typ = typeof(TestPerson);
        var result = typ.IsNullable();
        Assert.IsTrue(result);
    }

    [TestMethod]
    public void IsNullable_Decimal_ShouldReturn_False()
    {
        var typ = typeof(decimal);
        var result = typ.IsNullable();
        Assert.IsFalse(result);
    }

    [TestMethod]
    public void IsNullable_Byte_ShouldReturn_False()
    {
        var typ = typeof(byte);
        var result = typ.IsNullable();
        Assert.IsFalse(result);
    }

    [TestMethod]
    public void IsNullable_KeyValuePair_ShouldReturn_False()
    {
        var typ = typeof(KeyValuePair<string, string>);
        var result = typ.IsNullable();
        Assert.IsFalse(result);
    }

最简单的检查方法是某个Type是Nullable（包括字符串）

2 个答案: