public async Task <IEnumerable <long> > GetNextIDAsync(string context, int count = 1)
{
if (count <= 0)
{
throw new ArgumentException("must be greater than 0", nameof(count));
}
var lastID = 0L;
await this.EnsureRecordAsync(context);
using (var dbContext = new IdentityDbContext(this.options))
using (var dbTransaction = dbContext.Database.BeginTransaction())
{
try
{
var retryCount = 5;
do
{
var record = dbContext.Identity.SingleOrDefault(record => record.Context == context);
record.NextID += count;
var result = await dbContext.SaveChangesAsync();
if (result == 1)
{
dbTransaction.Commit();
lastID = record.NextID;
break;
}
} while (--retryCount > 0);
}
catch
{
dbTransaction.Rollback();
}
}
var next = new long[count];
for (int start = 0; start < count; ++start)
{
next[next.Length - start - 1] = lastID - start;
}
return(next);
}
private async Task EnsureRecordAsync(string context)
{
using IdentityDbContext dbContext = new IdentityDbContext(this.options);
var retryCount = 5;
do
{
var record = dbContext.Identity.SingleOrDefault(record => record.Context == context);
if (record == null)
{
var identityID = 1L;
if (dbContext.Identity.Any())
{
identityID = dbContext.Identity.Max(record => record.ID) + 1;
}
record = new Identity
{
ID = identityID,
Context = context,
NextID = 0
};
await dbContext.AddAsync(record);
var result = await dbContext.SaveChangesAsync();
if (result == 1)
{
return;
}
}
else
{
return;
}
} while (--retryCount > 0);
throw new Exception($"Failed to fetch the record for the {context}");
}