May 06

Error making asyn call in Entity Framework: There is already an open DataReader associated with this Command which must be closed first

Using Entity Framework 6.0 I got this message. This problem occurs when mostly in Async environment. This is due to a reader (in the same DBContext) that is still open, while another reader tries to open an new one. Typically this is a async issue.

In my MVC 5 app I have a Async call to my webapi. My problem was that I created a second repository object in a method, while the first repository was created by Unity Dependency Injection Framework was not finished reading.

My solution:

In stead of newing the repository up in the method I injected it in the constructor and all issues where solved.

A better solution:

Add MultipleActiveResultSets=True to the connectionstring of the database.

Dec 24

Typescript Common errors and issues for newbies

Recently I started working with Typescript. I’ve noticed that I made some Typescript Common errors and issues for newbies. So I’ve deceided to blog about them. I hope others can benefit from this:

Error 1:
Javascript critical error at line X, column Y, in http…./yourfile.ts
SCRIPT1004: Expected ‘;’

Solution 1:
You’ve probably included the .ts (TypeScript) file in your HTML. But you must include the generated .js (JavaScript) file. Replace the .TS extention for .JS extention, compile the project and you’re all set.

Error 2:
Unhandled exception at line X, column Y in http://localhost/…..yourfile.js.

0x800a138f – JavaScript runtime error: Unable to get property ‘YOURCLASS’ of undefined or null reference

Solution 2:
You’ve probably NOT include the .js file in your HTML file. Include the file <script scr=”YOURFILE.js”></script> in the HTML page.

Error 3: (this error occurs at Typescript compile time, in the editor, at compile time)
Invalid ‘new’ expression

Solution 3:
You must include the correct namespace for the class to create:

Wrong: new Project();
OK: new MySolution.Classes.Project()

Error 4: (this error occurs in the editor, at compile time)
The property XX does not exists on value of type YY

Example code:
public Project: Myapp.Models.ProjectInfo;

Solution 4:
Although you’ve probably used Intellisense when editing. Still this error does appear. You must include a reference to the .ts file. Put the following line at top of the Typescript file that generates this error:

/// <reference path=”PATH TO YOUR TS CLASS FILE”/>

Error 5:
Supplied parameters do not match any signature of call target: type ‘XYX’ is missing property ‘concat’ from type ‘XYX[]’

Solution 5
The parameter expected is an array of XYZ, but the passed parameter is XYZ. Replace the parameter with the correct one (should be an array in this case).

 

Hope these error messages and the solutions I have provided you, will give you a head start. In my case, most error gave me a terrible a headache.

Happy coding