public async Task Sample()
{
using (var store = new DocumentStore())
{
#region email
string email = "*****@*****.**";
User user = new User
{
Email = email
};
using (IDocumentSession session = store.OpenSession())
{
session.Store(user);
// At this point, the user document has an Id assigned
// Try to reserve a new user email
// Note: This operation takes place outside of the session transaction,
// It is a cluster-wide reservation
CompareExchangeResult <string> cmpXchgResult
= store.Operations.Send(
new PutCompareExchangeValueOperation <string>("emails/" + email, user.Id, 0));
if (cmpXchgResult.Successful == false)
{
throw new Exception("Email is already in use");
}
// At this point we managed to reserve/save the user email -
// The document can be saved in SaveChanges
session.SaveChanges();
}
#endregion
#region query_cmpxchg
using (IDocumentSession session = store.OpenSession())
{
var query = from u in session.Query <User>()
where u.Email == RavenQuery.CmpXchg <string>("emails/[email protected]")
select u;
var q = session.Advanced
.DocumentQuery <User>()
.WhereEquals("Email", CmpXchg.Value("emails/[email protected]"));
}
#endregion
}
}
public static bool GetValueFromExpressionWithoutConversion(Expression expression, out object value)
{
switch (expression.NodeType)
{
case ExpressionType.Constant:
value = ((ConstantExpression)expression).Value;
return(true);
case ExpressionType.MemberAccess:
value = GetMemberValue(((MemberExpression)expression));
return(true);
case ExpressionType.MemberInit:
var memberInitExpression = ((MemberInitExpression)expression);
value = Expression.Lambda(memberInitExpression).Compile().DynamicInvoke();
return(true);
case ExpressionType.New:
value = GetNewExpressionValue(expression);
return(true);
case ExpressionType.Lambda:
var lambda = ((LambdaExpression)expression);
value = lambda.Compile().DynamicInvoke();
return(true);
case ExpressionType.Call:
if (expression is MethodCallExpression mce)
{
if (mce.Method.DeclaringType == typeof(RavenQuery) &&
mce.Method.Name == nameof(RavenQuery.CmpXchg))
{
if (TryGetMethodArguments(mce, out var args) == false)
{
value = null;
return(false);
}
value = CmpXchg.Value((string)args[0]);
return(true);
}
}
value = Expression.Lambda(expression).Compile().DynamicInvoke();
return(true);
case ExpressionType.Convert:
var unaryExpression = (UnaryExpression)expression;
if (unaryExpression.Type.IsNullableType())
{
return(GetValueFromExpressionWithoutConversion(unaryExpression.Operand, out value));
}
value = Expression.Lambda(expression).Compile().DynamicInvoke();
return(true);
case ExpressionType.NewArrayInit:
var expressions = ((NewArrayExpression)expression).Expressions;
var values = new object[expressions.Count];
value = null;
if (expressions.Where((t, i) => !GetValueFromExpressionWithoutConversion(t, out values[i])).Any())
{
return(false);
}
value = values;
return(true);
case ExpressionType.NewArrayBounds:
value = null;
expressions = ((NewArrayExpression)expression).Expressions;
var constantExpression = (ConstantExpression)expressions.FirstOrDefault();
if (constantExpression == null)
{
return(false);
}
if (constantExpression.Value.GetType() != typeof(int))
{
return(false);
}
var length = (int)constantExpression.Value;
value = new object[length];
return(true);
default:
value = null;
return(false);
}
}
