c# - 如何在 C# 中将 IEnumerable 列表转换为数据表

Question

我遇到了以下问题:

我通常使用下面的函数将自定义数据传输到 DataTable，但在这种情况下，输入数据是由列表组成的类。我只需要在 DataTable 中写入每行每个列表的第一个元素。你能帮我调整一下这个功能来实现吗？

public List<int> xID { get; set; }
public List<string> xName { get; set; }
public List<string> xType { get; set; }
public List<string> xSource { get; set; }
public List<int> xmdID { get; set; }
public List<string> xMDName { get; set; }
public List<string> xUser { get; set; }

public static DataTable ListToDataTable<T>(IEnumerable<T> list)
{
    Type type = typeof(T);
    var properties = type.GetProperties();

    DataTable dataTable = new DataTable();
    foreach (PropertyInfo info in properties)
    {
        dataTable.Columns.Add(new DataColumn(info.Name, info.PropertyType));
    }

    foreach (T entity in list)
    {
        object[] values = new object[properties.Length];
        for (int i = 0; i < properties.Length; i++)
        {
            values[i] = properties[i].GetValue(entity);
        }

        dataTable.Rows.Add(values);
    }

    return dataTable;
}

---

根据 Carra 的回答，我尝试了下面的代码，但它无法识别 pType 类型(找不到类型或命名空间名称“pType”(您是否缺少 using 指令或程序集引用？))

var v = properties[i].GetValue(entity);
Type pType = properties[i].PropertyType;

if (pType.IsGenericType && pType.GetGenericTypeDefinition() == typeof(Nullable<>))
pType = Nullable.GetUnderlyingType(pType);

                if (pType.IsEnum)
                    pType = Enum.GetUnderlyingType(pType);

                if (v.GetType().GetGenericTypeDefinition() == typeof(List<>))
                {
                    values[i] = (v as List<pType>).First();
                }

---

更新

我想这不是最好的解决方案，因为它不接受任何列表类型，但这是我能做的最好的解决方案:

    public static DataTable ListToDataTable<T>(IEnumerable<T> list)
    {
        Type type = typeof(T);
        var properties = type.GetProperties();

        DataTable dataTable = new DataTable();
        foreach (PropertyInfo info in properties)
        {
            Type propertyType = info.PropertyType;

            if (propertyType.IsGenericType | propertyType.GetGenericTypeDefinition() == typeof(Nullable<>) | propertyType.IsEnum)
                propertyType = propertyType.GetGenericArguments()[0];

            dataTable.Columns.Add(new DataColumn(info.Name, propertyType));
        }

        foreach (T entity in list)
        {
            object[] values = new object[properties.Length];
            for (int i = 0; i < properties.Length; i++)
            {
                var v = properties[i].GetValue(entity);
                Type pType = v.GetType().GetGenericArguments().FirstOrDefault();

                if (v.GetType().GetGenericTypeDefinition() == typeof(List<>))
                {
                    if(pType == typeof(int))
                        values[i] = (v as List<int>).First();
                    else if(pType == typeof(string))
                        values[i] = (v as List<string>).First();
                }
                else
                {
                    values[i] = v;
                }
            }
            dataTable.Rows.Add(values);
        }
        return dataTable;
    }

Answer 1

你需要这样的东西:

foreach (PropertyInfo info in properties)
{
    if(info.PropertyType == typeof(IEnumerable))
    {
       dataTable.Columns.Add(new DataColumn(info.Name, info.Cast<object>().First().GetType());
    }
    else
    {
       dataTable.Columns.Add(new DataColumn(info.Name, info.PropertyType));
    }
}

foreach (T entity in list)
{
    object[] values = new object[properties.Length];
    for (int i = 0; i < properties.Length; i++)
    {
        var v = properties[i].GetValue(entity);
        if(v is IEnumerable)
        {
          values[i] = (v.Cast<object>().First()).First();
        }
        else
        {
          values[i] = v;
        }
    }

    dataTable.Rows.Add(values);
}