/// <summary>
/// Convert and execute a query only if the <see cref="IQueryable"/> expression is not supported by the query provider.
/// </summary>
/// <param name="query">Query to execute.</param>
/// <param name="maxResults">The max number of results allowed in a single transaction against a persistence provider.</param>
/// <param name="convertedResult">The result of the query.</param>
/// <param name="numberOfTempResults">The number of temporary results that should be combined.</param>
/// <returns>A <see cref="bool"/> that specify if the query was converted and executed.</returns>
public static bool ConvertionIsRequiredAsExpressionIfNotSupported(IQueryable query, int maxResults, out object convertedResult, out int numberOfTempResults)
{
var vistor = new MethodExpressionsMarker();
var methodsNames = vistor.Eval(query.Expression);
var providerName = query.Provider.GetType().Name;
numberOfTempResults = 1;
List <string> knownUnsupportedFunctions;
if (unsupportedMethodsPerProvider.TryGetValue(providerName, out knownUnsupportedFunctions))
{
if (knownUnsupportedFunctions.Intersect(methodsNames).Count() > 0)
{
var adapter = new QueriableProviderAdapter()
{
Provider = query.Provider, MaxCollectionSize = maxResults
};
convertedResult = adapter.Eval(query.Expression, out numberOfTempResults);
return(true);
}
}
try
{
var enumerator = query.GetEnumerator();
enumerator.MoveNext();
convertedResult = null;
return(false);
}
catch (NotSupportedException ex)
{
var unsupportedMethod = ex.Message.Split(' ').Intersect(methodsNames).FirstOrDefault();
if (!string.IsNullOrEmpty(unsupportedMethod))
{
unsupportedMethodsPerProvider.AddOrUpdate(
providerName,
(_) => new List <string>()
{
unsupportedMethod
},
(_, lst) =>
{
lst.Add(unsupportedMethod);
return(lst);
});
}
var adapter = new QueriableProviderAdapter()
{
Provider = query.Provider, MaxCollectionSize = maxResults
};
convertedResult = adapter.Eval(query.Expression, out numberOfTempResults);
return(true);
}
}
/// <summary>
/// Execute the query. If it is not supported by the underlying query provider, transform it to be executed on a memory collection.
/// </summary>
/// <typeparam name="TResult">Type of the result.</typeparam>
/// <param name="expression">The expression tree to execute.</param>
/// <returns>The expression execution result.</returns>
public TResult Execute <TResult>(Expression expression)
{
try
{
return(this._underlyingProvider.Execute <TResult>(this.InterceptExpr(expression)));
}
catch (NotSupportedException)
{
var adapter = new QueriableProviderAdapter()
{
Provider = this._underlyingProvider, MaxCollectionSize = this.MaxResults
};
var res = adapter.Eval <TResult>(expression, this.Combiner);
return(res);
}
}
/// <summary>
/// Execute the query. If it is not supported by the underlying query provider, transform it to be executed on a memory collection.
/// </summary>
/// <param name="expression">The expression tree to execute.</param>
/// <returns>The expression execution result.</returns>
public object Execute(Expression expression)
{
try
{
return(this._underlyingProvider.Execute(InterceptExpr(expression)));
}
catch (NotSupportedException)
{
var adapter = new QueriableProviderAdapter()
{
Provider = _underlyingProvider, MaxCollectionSize = MaxResults
};
int numberOfTempResults;
var res = adapter.Eval(expression, out numberOfTempResults, Combiner);
return(res);
}
}