/// <summary>
/// Determine if the requested lock can be acquired
/// </summary>
/// <remarks>This does not hold any locks outside of the call, making it less expensive for probing locks.</remarks>
/// <returns>0 if the lock can't be granted, 1 if it can be.</returns>
public int PeekApplicationLock(string name, SqlLockMode lockMode)
{
int result;
using (var command = CreateCommand("SELECT APPLOCK_TEST('public', @Resource, @LockMode, @LockOwner)", GetConnection(), CommandType.Text, true))
{
CreateParameter(command, "Resource", DbType.String, ParameterDirection.Input, 255, name);
CreateParameter(command, "LockMode", DbType.String, ParameterDirection.Input, 32, lockMode.ToString());
CreateParameter(command, "LockOwner", DbType.String, ParameterDirection.Input, 32, "Session");
result = ExecuteScalar <int>(command, false);
}
return(result);
}
/// <summary>
/// Attempt to get the specified lock in the database, which will remain associated with this object
/// </summary>
/// <param name="name"></param>
/// <param name="lockMode"></param>
/// <param name="lockTimeoutMilliseconds"></param>
/// <returns>0 if the lock was granted, 1 if it was granted only after waiting, negative numbers for various failures.</returns>
public int GetApplicationLock(string name, SqlLockMode lockMode, int lockTimeoutMilliseconds)
{
//if necessary bump out our query timeout
if (lockTimeoutMilliseconds > 0)
{
var lockSeconds = lockTimeoutMilliseconds / 1000;
_queryTimeout = Math.Max(lockSeconds, _queryTimeout);
}
using (var command = CreateCommand("sys.sp_GetAppLock", GetConnection(), CommandType.StoredProcedure, true))
{
var transaction = _transaction;
if (transaction == null)
{
if (command.Connection.State != ConnectionState.Open)
{
command.Connection.Open();
}
transaction = command.Connection.BeginTransaction();
}
command.Transaction = transaction;
CreateParameter(command, "Resource", DbType.String, ParameterDirection.Input, 255, name);
CreateParameter(command, "LockMode", DbType.String, ParameterDirection.Input, 32, lockMode.ToString());
CreateParameter(command, "LockOwner", DbType.String, ParameterDirection.Input, 32, "Transaction");
CreateParameter(command, "LockTimeout", DbType.String, ParameterDirection.Input, 32, lockTimeoutMilliseconds.ToString());
var returnValue = CreateParameter(command, "ReturnValue", DbType.Int32, ParameterDirection.ReturnValue);
command.CommandTimeout = _queryTimeout;
ExecuteNonQuery(command, false);
if ((returnValue.Value == null) || (returnValue.Value == DBNull.Value))
{
transaction.SafeDispose();
return(-100);
}
else
{
_transaction = transaction; //since this is the true scope of our lock.
return((int)returnValue.Value);
}
}
}
