Author: chriseyre2000

Rules for Object Composition

~ chriseyre2000 ~ Leave a comment

I have found the following rules make reuse easier:

  1. Contained objects should not be aware of the container.
  2. Containers should be aware of the contents.
  3. Event handlers should be used for communication from the contained to the container.
  4. Inter object event handlers should be established by the Container and should be explicitly set up in code.

These simple rules permit reuse of the contained control.  Objects developed along these lines are much easier to extend and reuse.  It also makes it very quick to rearrange the top level container. 

These rules also apply recursively so that a container may be contained in an outer container. 

Boo and MSBuild

~ chriseyre2000 ~ Leave a comment

Msbuild is microsofts answer to Ant. This is a build tool for the .Net Platform.

It has the minor benfit of being the native file format of the Visual Studio 2005 project files.

You need the .Net Framework 2 installed and to add the Microsoft Framework to your path statement

Boo is a lightweight .Net language.

Here is a sample that gets a task written in Boo for msbuild:

=== MyTask.boo ===

import Microsoft.Build.Framework

import Microsoft.Build.Utilities

import Boo.Lang



class MyTask(Task):

    public override def Execute():

        Log.LogMessage(MyProperty)

            return true



    private _MyProperty as string



    MyProperty as string:

        get:

                    return _MyProperty

             set:

                    _MyProperty = value

=== Test.proj ===

<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003" 

         DefaultTargets="MyTarget"

         InitialTargets="BuildMyTask"

>

    

    <Target Name="BuildMyTask">

        <Exec command="booc MyTask.boo -t:library"/>

    </Target>



    <UsingTask TaskName="MyTask" AssemblyFile="MyTask.dll"/>



    <Target Name="MyTarget">

        <MyTask MyProperty="Hello!"/>

    </Target>

</Project>

===

You also need Boo installed (and on your path).

Copy Boo.Lang into the directory that you created these scripts in.



At the command line type: msbuild

This will build and run the minimal boo task.

I am planning to add a real msbuild task for boo.

Why is it so hard to move data from Excel to SQL Server?

~ chriseyre2000 ~ Leave a comment

Business users love Excel.  It is there prefered format of data.

If you can get report data into Excel then they rarely require other reports.

The problem comes when you want to take data the other way.

I have an application that has it’s business logic implemented as a set of stored procedures.  It is a data transformation application so this is the best place to do this.

We need to source certain data from Excel.  OPENDATASOURCE is the recommended solution as follows:

SELECT *
FROM OpenDataSource( 'Microsoft.Jet.OLEDB.4.0',
  'Data Source="c:Financeaccount.xls";User ID=Admin;Password=;Extended properties=Excel 5.0')...xactions

Aside from the drive mapping problems that you can get when the data is not on a local drive on the server there are the following issues:

Data types are implied from the data.  When you let Excel guess it has a better than 50% chance of being wrong.

If there are empty columns for a few rows it assumes the entire row is NULL. 

These two can be complete showstoppers.

The only solution was to move to feeding the data from access… 

Code Sample for Datasets and DataGridViews

~ chriseyre2000 ~ Leave a comment
        public Form1()
        {
            InitializeComponent();
            SqlConnection cnt = new SqlConnection(GetConnectionString());

            cnt.Open();
            SqlCommand cmd = cnt.CreateCommand();
            cmd.CommandText = “select * from Orders; select * from [Order Details]”;
            northwind.Load( cmd.ExecuteReader(), LoadOption.OverwriteChanges, “Orders”,”Order Details”);
            cnt.Close();
        }

        static private string GetConnectionString()
        {
            // To avoid storing the connection string in your code,
            // you can retrieve it from a configuration file, using the
            // System.Configuration.ConfigurationSettings.AppSettings property
            return “Data Source=(local);Initial Catalog=Northwind;”
                + “Integrated Security=SSPI;”;
        }

        private void dataGridView1_RowEnter(object sender, DataGridViewCellEventArgs e)
        {
            string s = dataGridView1.Rows[e.RowIndex].Cells[0].Value.ToString();
            orderDetailsBindingSource.Filter = “OrderId=” + s;
        }

Software Requirement Specifications

~ chriseyre2000 ~ Leave a comment

I have been working on a number of SRS’ lately. These do help in the developement of the application. At least you have a formal definition of what the project is trying to do.

A SRS helps in the development of the test plan.

Recently we have found one slight flaw. If the customer does not read the SRS it’s value decreases significantly. If the customer is not interested in reading a large formal document then a few small technical memos would have a greater chance to be read.

SQL Server Error handling problems part 2

~ chriseyre2000 ~ Leave a comment

SQL Server 2000 has even more error handling problems than I blogged about before.

It would appear that error handling has not been thought through at all.

Take the RAISERROR command as an example. This appears to be a very elegant means of raising errors to the user.  You only need to use sp_addmessage to register a new message. The problem is that the messages are server global.

This means that if you server is ever to host a third party application you cannot safely define your own messages for fear of a third party app stamping all over them.  This should be scoped at a database level, providing at least some control.

The more I look at sql server error handling the more depressed I get.