Question

I have written a project by ASP.NET and C# which uses dataset for connecting to database.
I want to test my code by when I create a unit test for my classes which use dataset I get following error:

Test method Test.CommodityRepositoryTest.GetCommoditiesTest threw exception: 
System.NullReferenceException: Object reference not set to an instance of an object.
at Terminal.Database.TransportCo.TransportCoTableAdapters.ConfigurationTableAdapter.InitConnection() in TransportCoDataSet.Designer.cs: line 12259
at Terminal.Database.TransportCo.TransportCoTableAdapters.ConfigurationTableAdapter.get_Connection() in TransportCoDataSet.Designer.cs: line 12144
at Terminal.Database.TransportCo.TransportCoTableAdapters.ConfigurationTableAdapter.InitAdapter() in TransportCoDataSet.Designer.cs: line 12227
at Terminal.Database.TransportCo.TransportCoTableAdapters.ConfigurationTableAdapter.get_Adapter() in TransportCoDataSet.Designer.cs: line 12133
at Terminal.Database.TransportCo.TransportCoTableAdapters.ConfigurationTableAdapter.GetData() in TransportCoDataSet.Designer.cs: line 12290

I have to mention that I use singleton repository but it does not change anything in the error.

does anyone has any idea?

these are my code and its test:

public List<Commodity> GetCommodities()
    {         
        var commoditySet=new CommodityTableAdapter();
        var commoditys = commoditySet.GetCommdity().ToList();
        if (commoditys.Count() == 0)
            throw new UserInterfaceException("هیچ کالایی در سیستم ثبت نشده است");
        var commoditiesName = new List<Commodity>();
        for (int i = 0; i < commoditys.Count(); i++)
            commoditiesName.Add(ConvertcommodityRowTocommodity(commoditys[i]));
        return commoditiesName;
    }





   [TestMethod()]
    public void GetCommoditiesTest()
    {
        var target = CommodityRepository.GetInstance(); // TODO: Initialize to an appropriate value
        var expected = new List<Commodity> {new Commodity() {HSCode = "323423", ID = 19}}; // TODO: Initialize to an appropriate value
        List<Commodity> actual = target.GetCommodities();
        Assert.AreEqual(expected[0].ID, actual[0].ID);            
        //Assert.Inconclusive("Verify the correctness of this test method.");
    }

Answer 1

Your typing is ambiguous

var commoditys = commoditySet.GetCommdity().ToList();

use insteand explicit types

Object commoditys = commoditySet.GetCommdity().ToList();

then you will receive appropriate debugging errors.