clickable tr and Show/Hide Panel

vijeyashobana — Tue, 28 Apr 2009 19:32:34 +0000

Sometimes we may need to code to make an entire row clickable, I mean, the user should click any cell on a tr and a required functionality should be performed as the result of this click. When you cannot use server side coding and rely entirely on client side coding, the below could be one of the approaches to this problem.

Name	Title	Phone Number	Email
Bill	Gates	800-000-0000	bill.gates@microsoft.com
Bill	O’Reilly	800-000-0000	bill.reilly@foxnews.com

Javascript functions inside

coming back to markup:

in my case, i want to show a panel when a tr is clicked, this panel will contain detailed information relevant to the . this panel would be initially hidden, and when the is clicked, will be displayed.

                    //empty

Address

none

Name

, value will be dynamically displayed using

// string keyString – this keyString serves as a key to the ‘javascriptString’. This means I can use one keystring for the same function anywhere in the code to call the page refresh javascript function.

The ‘functionToRefresh()’ should be entered in the .aspx page and the above code should be entered in the .aspx.cs. Thats it. I include these 2 snippets in any page I want to refresh. Whenever after any task is performed, if i want a page refresh I’ll iclude these 2 code pieces.

Money and Date display

vijeyashobana — Sat, 02 Aug 2008 23:46:34 +0000

Very often we are required to display date and money values on the webpages. In the SQL Server database, the date is stored as SQLDBType.Datetime and the currency values are stored as SBLDBType.Money.

In the C# code, the SQLDBType.Datetime should be converted to System.DateTime and SBLDBType.Money to System.decimal:

Datetime d = Convert.ToDateTime( SBLDBType.DateTime variable);

decimal m = Convert.ToDecimal( SBLDBType.Money variable);

In the Source page, these values can be displayed as:

<%# DataBinder.Eval(Container.DateItem, “Money”, “{0:c}” %> //here Money is column name

<%# DataBinder.Eval(Container.DateItem, “date”, “{0:d}” %> //here date is column name

provided the values are coming from database.

In the code-behind, these values can be defined as:

label1.Text = String.Format(“{0:c}”, SQLmoneyVariable)

label2.Text = String.Format(“{0:d}”, SQLdateVariable)

This will cause the labels to display money and date values on the webpage. String.Format is used to return the date and currency values as string in the required format.

Data-binding expressions

vijeyashobana — Fri, 04 Jul 2008 23:25:53 +0000

When working with Databound controls, very often we are required to work with templates, may be they are ItemTemplates, EditItemTemplates, InsertItemTemplates etc. In these situations usually we’ll use data-binding expressions.

There are 3 types of commonly used Data-binding expressions.

1. Type I – <%# Eval(“column_name”) %>

The above expression is a 2-way expression, meaning you can read/write values. Commonly used in TextBoxes.

‘<%# Eval(“LastName”) %>

2. Type II – <%# Bind(column_name) %>

The above expression is a 1-way expression, meaning you can only read values. Commonly used in DropDownLists, Listboxes, labels.

3. Type III – <%# Function() || variable %>

Examples: <%# SomeMethod() %>

<%# firstName %>

<%# (firstname)+’ ‘+(lastname) %>

Reference: http://msdn.microsoft.com/en-us/library/ms178366(VS.80).aspx, http://bhaidar.net/cs/archive/2006/08/04/473.aspx

JOIN in DataSets – Good idea or bad idea?

vijeyashobana — Fri, 04 Jul 2008 22:38:54 +0000

Very often we programmers are needed to use JOIN statements in our code. We use JOINs to configure DataSource controls, populate Datasets, etc.

SELECT statements would be used to join 2,3 or more tables. So far so good. But problem arises when using UPDATE, DELETE, INSERT statements. It is not possible to update 2 or more tables in one statement. Also UPDATE, INSERT, DELETE statements would not be automatically generated when configuring the data source. The programmer has to code these statements.

To avoid these difficulties and to make our lives easy, it is better to use subqueries in SELECT statements. When configuring the data source, there is an easy way to make our lives better:

1. Use a SELECT statement on one table.

2. Click ‘Advanced’ tab and Check ‘Automatically Generate INSERT, UPDATE, DELETE statements’.

Now Configure the same datasource again. Now use 1or more SELECT subqueries within the original subquery.

This would give us the same desired result like using JOINs. Also, INSERT, UPDATE, DELETE statements aer automatically generated for us.

SQL QUERY USING JOINS:

USE NORTHWIND

SELECT TOP 5 PDT.PRODUCTNAME, CAT.CATEGORYNAME, SUP.COMPANYNAME FROM CATEGORIES CAT
INNER JOIN PRODUCTS PDT ON CAT.CATEGORYID=PDT.CATEGORYID
INNER JOIN SUPPLIERS SUP ON SUP.SUPPLIERID = PDT.SUPPLIERID

Now the same result can be produced using the below SQL query:

USE NORTHWIND

SELECT TOP 5 PRODUCTNAME,
(SELECT CATEGORYNAME FROM CATEGORIES WHERE CATEGORIES.CATEGORYID=PRODUCTS.CATEGORYID) AS CATEGORYNAME,
(SELECT COMPANYNAME FROM SUPPLIERS WHERE SUPPLIERS.SUPPLIERID = PRODUCTS.SUPPLIERID) AS SUPPLIERNAME
FROM PRODUCTS

Reference: Scott Mitchell’s Data Access Tutorials in www.asp.net

GridView and DataSource

vijeyashobana — Fri, 04 Jul 2008 21:03:36 +0000

GridView is built to work with DataSource. This DataSource can be either dataset or a DataSource control.

When using GV with DSet, you have to handle the Paging, Editing, Sorting functions.

When using GV with DSrc, the above functions are built-in for you. If you have a strict 3-tier architecture, use ObjectDataSource control.

Suppose I don’t use a primary key column in the SELECT statement for SqlDataSource. What would happen in that case?

I tried it and in the UPDATE command i set the condition to check for a specific primary key value but the catch is there is no PK in SELECT statement. When I tried to run this code, I didn’t get any error. I was able to click ‘EDIT’ button of GridView, enter new information and UPDATE it. However the thing is no info was updated. It didn’t show any error but it didnt give the desired result either.

So have one column as PK. If you didn’t select any PK column, at least set the DataKeys value to a column name. This way the column will be made a PK column for the datatable.

DataSet Editing

vijeyashobana — Mon, 30 Jun 2008 20:50:51 +0000

It seems so easy to say the data in dataset can be edited and updated to the database. But in reality there are abundant problems surrounding this single concept. This is because there are numerous different situations pertaining to this simple concept. Some are, what if the underlying table has no primary key? what if the underlying table is a result of join on 2 different tables? what if the underlying table does have a primary key? Will the dataset created in a Button_Click be carried over to the other events of the gridview/ any databound control for that matter? What about AcceptChanges(), BeginEdit()?

We will analyze every question one by one here.

what if the underlying table has no primary key?

if the dataTable of Dataset has no PK , manually set a PK on any column of the dataTable.

dset.Tables[0].PrimaryKey = new System.Data.DataColumn[] { dset.Tables[0].Columns[1] };

To have more than 1 column as a PK, i.e, composite PK, use :

dset.Tables[0].PrimaryKey = new System.Data.DataColumn[] { dset.Tables[0].Columns[1] , dset.Tables[0].Columns[2]};

Remember, PrimaryKey property returns a DataColumn[]. So you need to set a DataColumn array value to it otherwise it throws an error.

what if the underlying table is a result of join on 2 different tables?

if the Dtbl is a result of join, then the DataTable will not have any PK on it. In this case, you have to manually set it.

what if the underlying table does have a primary key?

This usually happens if the DataTable is a result of some SELECT statement and the SELECT statement gives a column set as PK. So in this case, we have to make sure the CONSTRAINTS info is updated in the dataset. This is because when you call a SELECT statement, the schema info is not added to the dataset. It should be done manually thus:

da.FillSchema(dset, SchemaType.Source, “Authors”);

if you didn’t use the above statement, you can also use the below one:

da.MissingSchemaAction = MissingSchemaAction.AddWithKey;

If you manually set the PK on the underlying DaTbl, donot use the above code. If you use both, it will throw exception.

Will the dataset created in a Button_Click be carried over to the other events of the gridview/ any databound control for that matter?

No. the dset will not be carried over. So you have to have a method to fill the dataset and call that method in your other DataBound events.

What about AcceptChanges(), Begin/EndEdit()?

To make changes in any DataRow, I need to create a new DataRow. But I cannot use DataRow() because this cannot be used. You need to use

DataRow dr = dt.NewRow();

and assign the dr with the required row,

dr = dt.Rows.Find(“Aria Cruz”);

Following the above,

dr.BeginEdit();
dr["EMPLOYEE_NAME"] = “Aria Tamil”; //changed the original name to Aria Tamil
dr.EndEdit();
dset.AcceptChanges(); //committing the dataset with the changes
da.Update(dset); //pass the changed dataset to d/b

My Experiments with code

clickable tr and Show/Hide Panel

Money and Date display

Data-binding expressions

JOIN in DataSets – Good idea or bad idea?

GridView and DataSource

DataSet Editing