Using Viewstate for Saving datatable in asp.net c#

Using a viewstate to save a datatable is useful for developting shopping cart applications. In such a case we have to keep track of all the products that has been selected by the customer on a particular session. For this we use a combination of view state or session to hold the product information in datatable.

Creating a DataTable and saving it on the view state :

private void createMyDataTable()
{

DataTable dtCart = new DataTable();
DataColumn dc = new DataColumn();
DataColumn dc1 = new DataColumn();
DataColumn dc2 = new DataColumn();

dc.DataType = Type.GetType("System.Int32");
dc.ColumnName = "Id";
dc.AutoIncrement = true;
dc.AutoIncrementSeed = 1;
dtCart.Columns.Add(dc);
dc1.DataType = Type.GetType("System.String");
dc1.ColumnName = "ProductName";
dtCart.Columns.Add(dc1);
dc2.DataType = Type.GetType("System.Int32");
dc2.ColumnName = "Price";
dtCart.Columns.Add(dc2);

ViewState["dtMyCart"] = dtCart;

}
from the above code we can create a structure of a datatable which can hold the information of the products selected by the client. Once the structure of the table is created we have to save the datatable to a viewstate object. This is done to acess the table later in the page.

Once the datatable structure is saved on our viewstate, we can start using the datatable for saving products. Procedure for adding a new product is as follows

private void addDataToMyTable(string paramProductName, int paramProductId, Int32 paramPrice)
{
MyNewDataTable = (DataTable)ViewState["dtMyCart"];
DataRow row;
row = MyNewDataTable.NewRow();
row["ProductName"] = paramProductName;
row["Id"] = paramProductId;
row["Price"] = paramPrice;


MyNewDataTable.Rows.Add(row);
ViewState["dtMyCart"] = MyNewDataTable;

}

Here in this function, we have four parameters each one has a value for the product. First of all we have to create an instance of the datatable from the viewstate after that we can start adding the product into the user cart.


with regards,
Praveen

Rowbound Property for Gridview Control

This can be a simple tutorial but I think it is useful for beginners. You can use this code snippet to dynamically change the value of an ImageButton while the row is being generated. It is useful in cases where we are listing Images of a product and we have to add a noimage pic ,if there is no image available.

protected void gvLastUpdated_RowDataBound(object sender, GridViewRowEventArgs e)
{
try
{
if (e.Row.RowType == DataControlRowType.DataRow)
{
ImageButton imgButton = (ImageButton)e.Row.FindControl("ImageButton1");

if (imgButton.ImageUrl.ToString().Trim() == "")
{
imgButton.ImageUrl = "~\\uploads\\noimage.jpg";
}
else
{
imgButton.ImageUrl = "~\\uploads\\" + imgButton.ImageUrl.ToString();

}
}
}
catch (Exception e1)
{
lblMessage.Text = (e1.ToString());
}
}

with Regards,
Praveen
http://www.linesandgraphs.com

Identifying controls in a row that generates an event in a datagrid control

suppose if we are using a Template control to place so many controls in a gridrow and we need to track the row from which control has generated an event in such a case we can use the following code.

protected void btnCart_Click(object sender, EventArgs e)
{
Button btn= (Button)sender;
GridViewRow grdRow =(GridViewRow) btn.Parent.Parent;
}

Here i have a button inside my template control and once i click my button from a data row i can create an object of the row that has generated the click event.

by using the grdRow instance you can acess the elements within that row.
Label lbProdTitle = (Label)(grdRow.Cells[0].FindControl("fldPropertyTitleLabel1"));
Label lbPrice = (Label)(grdRow.Cells[0].FindControl("fldPrice"));

with regards,
Praveen
www.linesandgraphs.com