Question

我该如何修改：

if ( reader.GetString( reader.GetOrdinal( "Status" ) ) == "Yes" )
{
    return true; // Return Status + Date it was Completed
}
else
{
    return false; // Return Status + null Date.
}

要返回两个值吗？目前，它从数据库中返回“状态”列，其值为“是”或“否”。如何让它返回完成的日期和状态？

Answer 1

    private void DoSomething() {
        string input = "test";
        string secondValue = "oldSecondValue";
        string thirdValue = "another old value";
        string value = Get2Values(input, out secondValue, out thirdValue);
        //Now value is equal to the input and secondValue is "Hello World"
        //The thirdValue is "Hello universe"
    }

    public string Get2Values(string input, out string secondValue, out string thirdValue) {
        //The out-parameters must be set befor the method is left
        secondValue = "Hello World";
        thirdValue = "Hello universe";
        return input;
    }

Answer 2

在我看来，这是最好的方法，为结果写一个类或结构。

否则你可以使用out-parameter

Answer 3

这是一个小例子：

    private void DoSomething() {
        string input = "test";
        string secondValue = "oldSecondValue";
        string value = Get2Values(input, out secondValue);
        //Now value is equal to the input and secondValue is "Hello World"
    }

    public string Get2Values(string input, out string secondValue) {
        //The out-parameter must be set befor the method is left
        secondValue = "Hello World";
        return input;
    }

Answer 4

最好定义一个带有两个属性的struct，但如果你真的不想这样做，你可以使用通用的KeyValuePair<TKey,TValue>结构：

        KeyValuePair<bool, DateTime?> result;
        if (reader.GetString(reader.GetOrdinal("Status")) == "Yes")
        {
            result = new KeyValuePair<bool, DateTime?>
                (true, DateTime.Now); // but put your date here
        }
        else
        {
            result = new KeyValuePair<bool, DateTime?>
                (false, null);
        }
        // reader.Close()?
        return result;

KeyValuePair有两个属性Key和Value。钥匙将是您的状态，价值将是您的日期。

注意，如果您需要空日期，则需要使用nullable DateTime。

返回两个值

4 个答案: