/// <summary>
/// 插入一个新的 Tag-FileItem 关系，并返回实体类对象。
/// 若关系已存在，则什么都不做。
/// </summary>
/// <returns>关系实体类</returns>
public async Task <TagFileRelation> AddRelationAsync(Tag tag, FileItem fileItem)
{
#if DISPOSE_CONTEXT_IMMEDIATELY
using (var context = Context)
{
#endif
var relation = await GetRelationAsync(tag, fileItem);
if (relation == null)
{
relation = new TagFileRelation
{
TagId = tag.TagId,
FileItemId = fileItem.FileItemId,
UtcCreateTime = DateTime.UtcNow
};
await context.Relations.AddAsync(relation);
await context.SaveChangesAsync();
}
return(relation);
#if DISPOSE_CONTEXT_IMMEDIATELY
}
#endif
}
/// <summary>
/// 移除 TagFileRelation 对象。
/// 若关系不存在则什么都不做。
/// </summary>
public async Task RemoveRelationAsync(TagFileRelation relation)
{
#if DISPOSE_CONTEXT_IMMEDIATELY
using (var context = Context)
{
#endif
if (await IsRelationExistAsync(relation.Tag, relation.FileItem))
{
context.Relations.Remove(relation);
await context.SaveChangesAsync();
}
#if DISPOSE_CONTEXT_IMMEDIATELY
}
#endif
}
