Support for .StartsWith with Sqlite Async #696
Description
I'm trying to do a search where the user enters a string then find a matching string in my db.
Currently, using .Contains() for the search works just fine. E.g.
User Input: Park
Results: Central Park, Washing Square Park, Riverside Park, Park Avenue, Park Chester
However, if I use .StartsWith() instead of .Contains(), it results in a null reference exception thrown.
var dbCode = await repo.GetAsync<List<DBCode>>(_ => _.Code.Equals(id) && _.Name.ToUpper().StartsWith(searchWord.ToUpper())); //Doesn't work, throws NRE
var dbCode = await repo.GetAsync<List<DBCode>>(_ => _.Code.Equals(id) && _.Name.ToUpper().Contains(searchWord.ToUpper())); //works fine
I want to use .StartsWith(), so I have the expected result below:
User Input: Park
Result: Park Avenue, Park Chester
Instead of all the words that end in park.
How can I do that with the approach I'm using above?
Exception details below:
System.NullReferenceException: Object reference not set to an instance of an object.
at SQLite.TableQuery`1.CompileExpr(Expression expr, List`1 queryArgs)
at SQLite.TableQuery`1.CompileExpr(Expression expr, List`1 queryArgs)
at SQLite.TableQuery`1.GenerateCommand(String selectionList)
at SQLite.TableQuery`1.GetEnumerator()
at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
at SQLite.AsyncTableQuery`1.<ToListAsync>b__9_0()
at System.Threading.Tasks.Task`1.InnerInvoke()
at System.Threading.Tasks.Task.Execute()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
at Data.SQLiteRepository`1.<GetAsync>d__3`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
As a side note, this issue also happens for .Trim() and some other linq commands as well.
Also, I am using the Generic Repository here in the first comment as well: https://stackoverflow.com/questions/29050400/generic-repository-for-sqlite-net-in-xamarin-project
Particularly:
public async Task<List<T>> GetAsync<TValue>(Expression<Func<T, bool>> predicate = null,
Expression<Func<T, TValue>> orderBy = null)
{
var query = Context.Table<T>();
if (predicate != null)
query = query.Where(predicate);
if (orderBy != null)
query = query.OrderBy<TValue>(orderBy);
return await query.ToListAsync();
}