Problem when trying to preview reports

[أشرف]

Greetings,

I'm using Telerik Reporting version 8.1.14.804 (Q2 2014 SP1) in an ASP.Net Web Forms application, inside Visual Studio 2012 (Ultimate 2012 Version 11.0.61030.00  Update 4).
I created a simple report that fetches data from an entity data source that uses a DbContext class in the project.

The report works as expected, but in design time, when I try to preview it, an error message is displayed saying:
An error has occurred while processing Table 'table1': An error occurred while
invoking data retrieval method. Try restarting Visual Studio. -------------
InnerException ------------- No connection string named 'DbContext' could be
found in the application config file.

Where DbContext is the name of my code first context class.

I uploaded a demo web application that demonstrates the problem here:
http://www.wikifortio.com/825288/ReportsSample.zip
I removed the bin directory but Nuget should settle this.

How to resolve this issue?

[Stef]

Hi Ashraf,

In the DbContext you need to add a second constructor accepting a string parameter, which will be used by the EntityDataSource component to pass the connection string from the component configuration.

namespace TelerikReportsPlayground.Data
{
    using System;
    using System.Data.Entity;
    using System.ComponentModel.DataAnnotations.Schema;
    using System.Linq;

    public partial class DbContext : System.Data.Entity.DbContext
    {
        public DbContext()
            : base("name=DbContext")
        {
        }

        public DbContext(string connstr)
            : base(connstr)
        {
        }

        public virtual DbSet<Department> Departments { get; set; }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
        }
    }
}

For more details please go through the EntityDataSource Component overview article.


Regards,
Stef
Telerik

 

 

[أشرف]

This resolves the problem. Thank you.

But I have a question: The documentation page you pointed me to says "If Code First is used there is no need for a constructor with string parameter" and I use code first in my project. I wonder what's the need for a connection string? Why not the designer just instantiate the DbContext and fetch data from it? Specially that the report works at run time without providing a connection string.

[Stef]

Hello Ashraf,

If you set your model as follows you can omit the second constructor, and specify the already existing model's connection string by name:

<!-- connectin string saved during creating the data model -->
 <connectionStrings>
    <add name="DbContext" connectionString="data source=.\SQLEXPRESS;initial catalog=AdventureWorks;Integrated Security=SSPI;MultipleActiveResultSets=True;App=EntityFramework" providerName="System.Data.SqlClient" />
  </connectionStrings>
......................
//the model settings
namespace TelerikReportsPlayground.Data
{
    using System;
    using System.Data.Entity;
    using System.ComponentModel.DataAnnotations.Schema;
    using System.Linq;

    public partial class DbContext : System.Data.Entity.DbContext
    {
        public DbContext()
            : base("DbContext")
        {
        }
................................
//the EntityDataSource component settings
            //
            // entityDataSource1
            //
            this.entityDataSource1.ConnectionString = "DbContext";
            this.entityDataSource1.Context = typeof(TelerikReportsPlayground.Data.DbContext);
            this.entityDataSource1.ContextMember = "Departments";
            this.entityDataSource1.Name = "entityDataSource1";
        public virtual DbSet<Department> Departments { get; set; }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
        }
    }
}

Regards,
Stef
Telerik