Issue with LinqToDb T4 templates for a SqlLite database (using LoadSQLiteMetadata)

Question

I'm trying to use a local SqlLite database (in my app_data) folder with LinqToDb.

Anybody an idea why LinqToDb cannot work with the following connectionstring ?

  <connectionStrings>
    <add name="RecyclesDB"
         providerName="System.Data.SqlLite"
         connectionString="data source=|DataDirectory|Recycles.sqlite3;Version=3;" 
         />
  </connectionStrings>

I can perfectly use this connectionstring to retrieve data the old-school way.

  SQLiteConnection sqlConn;
  var sqlCmd = new SQLiteCommand();
    using (sqlConn = new SQLiteConnection(ConfigurationManager.ConnectionStrings["RecyclesDB"].ConnectionString))
    {
      sqlConn.Open();
      sqlCmd.Connection = sqlConn;
 /* .... */               
    }

However, when I try to use LinqToDB with the following t4 template it fails

<#@ template language="C#" debug="True" hostSpecific="True"                           #>
<#@ output extension=".generated.cs"                                                  #>
<#@ include file="$(ProjectDir)LinqToDB.Templates\LinqToDB.SQLite.Tools.ttinclude" #>

<#@ include file="$(ProjectDir)LinqToDB.Templates\PluralizationService.ttinclude"     #>

<#
    NamespaceName = "RecycleDashboard";
    LoadSQLiteMetadata(LoadSQLiteMetadata(@"C:\inetpub\RecycleDashboard\app_data", "Recycles.sqlite3"););
    GenerateModel();
#>

To specify the issue. The T4 template generates the models alright, but when I try to use these with the following code I get a null reference

    using (var db = new RecyclesDB())
    {
        var recycles =
            (from recycle in db.AppRecycles
             select recycle).ToList();
    }

The exception on new RecyclesDB() is :

System.NullReferenceException was unhandled by user code
  HResult=-2147467261
  Message=Object reference not set to an instance of an object.
  Source=linq2db
  StackTrace:
       at LinqToDB.Data.DataConnection..ctor(String configurationString) in i:\linq2db\Source\Data\DataConnection.cs:line 41
       at LinqToDB.Data.DataConnection..ctor() in i:\linq2db\Source\Data\DataConnection.cs:line 24
       at RecycleDashboard.RecyclesDB..ctor() in 
 ...

Anybody an idea what's wrong here ?

AardVark71 · Answer 1 · 2015-12-06T13:46:50.690

OK, just in case anyone else stumbles over issues with the Sqlite Dataprovider too

I resolved this but specifying my DataConnection specifically as follows (GetDataProvider and GetConnection as suggested on https://github.com/linq2db/linq2db):

public partial class RecyclesDB : LinqToDB.Data.DataConnection
    {
    public RecyclesDB() : base(GetDataProvider(), GetConnection()) { }

    private static IDataProvider GetDataProvider()
    {
        return new LinqToDB.DataProvider.SQLite.SQLiteDataProvider();
    }

    private static IDbConnection GetConnection()
    {
        return new SQLiteConnection(ConfigurationManager.ConnectionStrings["RecyclesDB"].ConnectionString);
    }
}

Not sure why the code generated by the T4 template fails, but it looked like the LinqToDB DataConnection class couldn't resolve the dataprovidername 'System.Data.SQLite' automatically.

Issue with LinqToDb T4 templates for a SqlLite database (using LoadSQLiteMetadata)

1 Answers1