Question
I have some code written in C#. I am trying to write some generic code that I can reuse. My actual code is more complicated. However, the code is question looks like the following:
public async Task<T> ExecuteQueryAsync<T>(string sql)
{
var results = default(T);
using (var database = new SqlConnection("[ConnectionString]"))
{
database.Open();
results = await database.QueryAsync<T>(sql);
}
return results;
}
When I build my project, I get a compile-time error that says:
Cannot implicitly convert type 'System.Collections.Generic.IEnumerable<T>' to 'T'. An explicit conversion exists (are you missing a cast?)
I do not fully understand why I'm getting this error. I intend to call it in a manner like this:
Adapter adapter = new Adapter();
var results = await adapter.ExecuteQueryAsync<IEnumerable<Customer>>("SELECT * FROM Customer");
In the above, wouldn't T be an IEnumerable<T>? If that's the case, I do not understand why I'm getting this type conversion error at compile-time.
Thank you!
Accepted Answer
Try something like this.
public async Task<IEnumerable<T>> ExecuteQueryAsync<T>(string sql)
{
IEnumerable<T> results = Enumerable.Empty<T>();
using (var database = new SqlConnection("[ConnectionString]"))
{
database.Open();
results = await database.QueryAsync<T>(sql);
}
return results;
}
Popular Answer
In your ExecuteQueryAsync you not need it results variable, since you always rewrite it. So your function can be like this
public async Task<IEnumerable<T>> ExecuteQueryAsync<T>(string sql)
{
using (var database = new SqlConnection("[ConnectionString]"))
{
database.Open();
return await database.QueryAsync<T>(sql);
}
}
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