如何测试对象是否具有属性并进行设置？

Question

我在C＃中有此代码

        foreach (var entry in auditableTableEntries)
        {
            IAuditableTable table = (IAuditableTable)entry.Entity;
            table.ModifiedBy = userId;
            table.ModifiedDate = dateTime;
            if (entry.State == EntityState.Added || entry.State == EntityState.Modified)
            {
                if (table.CreatedBy == null || table.CreatedBy == null)
                {
                    table.CreatedBy = userId;
                    table.CreatedDate = dateTime;
                }
            }

        }

一些表对象具有属性modified，为此，我想将属性设置为秒数。自1970年以来。类似：

        table.modified = (int)(DateTime.UtcNow - new DateTime(1970, 1, 1)).TotalSeconds

但是，如何判断该表是否具有该属性？如果属性不存在，我不想设置该属性，因为我认为这会导致异常。

到目前为止，这是我尝试过的：

      if (table.GetType().GetProperty("modified") != null)
      {
          // The following line will not work as it will report that
          // an IAuditableTable does not have the .modified property

          table.modified = (int)(DateTime.UtcNow - new DateTime(1970, 1, 1)).TotalSeconds
      }

但这是问题，因为IAuditableTable不包含修改后的属性，所以table.modified是无效的语法。

Answer 1

使用反射：

PropertyInfo propInfo 
    = table.GetType().GetProperties(BindingFlags.Instance | BindingFlags.Public)
    .FirstOrDefault(x => x.Name.Equals("modified ", StringComparison.OrdinalIgnoreCase));

// get value
if(propInfo != null)
{
    propInfo.SetValue(table, DateTime.Now);
}

或者像其他人指出的那样，您最好让您的类实现另一个接口，例如IHasModified和：

if(table is IHasModified)
{
    (table as IHasModified).modified = //whatever makes you happy. ;
}