Using Visual Studio and Dapper, how do I use a connection string?
.net-core asp.net asp.net-mvc c# dapper
Question
I am trying to get a Connection String set up in my .Net Core application but i keep getting the error:
System.NullReferenceException: 'Object reference not set to an instance of an object.'
I have tried adding the following to appsettings.json:
"ConnectionStrings": {
"Analysis": "Server=DESKTOP-MYSERVER;Database=MYDATABASE;User Id=sa; Password=Password123;Provider=System.Data.SqlClient;Trusted_Connection=True;MultipleActiveResultSets=true;Pooling=false;"
}
I also tried using web.config like I used to before .Net Core:
<connectionStrings>
<add name="Analysis" providerName="System.Data.SqlClient"
connectionString="Server=DESKTOP-MYSERVER;Database=MYDATABASE;User Id=sm;Password=Password123;"/>
Then in c# i have:
public List<DapperTest> ReadAll()
{
var data = new List<DapperTest>();
using (IDbConnection db = new SqlConnection(ConfigurationManager.ConnectionStrings["Analysis"].ConnectionString))
{
data = db.Query<DapperTest>("select * from testTable").ToList();
}
return data;
}
Both ways give me the exception of:
System.NullReferenceException: 'Object reference not set to an instance of an object.'
I have used the following resources:
.Net CORE Dapper Connection String?
https://docs.microsoft.com/en-us/aspnet/core/data/ef-mvc/intro
Get connection string from App.config
But I am missing something. I have only set up connection strings once and it was not in .Net Core so it could be obvious to others.
Accepted Answer
If you are using appsettings.json, create a simple POCO class to model your connection string configurations like this:
public class ConnectionConfig
{
public string Analysis {get;set;}
}
Add this line in ConfigureServices method in Startup.cs
services.Configure<ConnectionConfig>(Configuration.GetSection("ConnectionStrings"));
Data service class
class YourClass{
private string _connectionString;
YourClass(string connectionString){
_connectionString = connectionString;
}
//Your implementation
public List<DapperTest> ReadAll()
{
var data = new List<DapperTest>();
using (IDbConnection db = new SqlConnection(_connectionString)
{
data = db.Query<DapperTest>("select * from testTable").ToList();
}
return data;
}
}
Inject IOptions<ConnectionConfig> in your controller constructor .
class YourController : Controller{
YourClass _testing;
YourController(IOptions<ConnectionConfig> connectionConfig){
var connection = connectionConfig.Value;
string connectionString = connection.Analysis;
_testing = new YourClass(connectionString );
}
public IActionResult Index() {
var testingData = _testing.ReadAll();
return View();
}
}
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