无法将int []类型隐式转换为int？[]

Question

在我的示例类中,它包含IdValues int?[].值来自具有Id作为关键字段的其他类.

//Database class
public class SampleValues // this is a entity that i want to collect the deatil id
{
    public int Id { get; set; }
    public int?[] SampleDetailIdValue { get; set; }
}

public class SampleDetailValues // this is the detail entity
{
    public int Id { get; set; }
}


// The error code
if (sampleDetails.Count > 0)
{
    sample.IdValues = sampleDetails.Select(s => s.Id).ToArray(); // << The error occurred this line.
}

错误是无法将类型隐式转换int[]为int?[]

Answer 1

投射你的投影:

sample.IdValues = sampleDetails.Select(s => (int?)s.Id).ToArray(); 

你正在投射一个int,ToArray给你打电话int[],所以简单地投射一个int?.

或者有Cast扩展方法:

sample.IdValues = sampleDetails
    .Select(s => s.Id) 
    .Cast<int?>()
    .ToArray();