Sunday, December 10, 2006

DataBinder.Eval() Method

DataBinder.Eval() Method

DataBinder.Eval() method saves you from writing complex expressions.

For example, make your datagrid column to template field.

Now, lets understand it various use with different example.


Example1: Concat two datagrid column into one.

In .ASPX File
asp:TemplateColumn HeaderText="Address"
ItemTemplate
asp:Label id="Label1" runat="server" Text='%#

ConcatColumns(DataBinder.Eval(Container.DataItem,"City"),DataBinder.Eval(Container.DataItem,

"Country")) %'lblAddress/asp:Label
/ItemTemplate
/asp:TemplateColumn

In .CS File
public static string ConcatColumns(object objText1, object objText2)
{
return objText1.ToString() + " " + objText2.ToString();
}



Example2: Opening a default Email Program on clicking datagrid column.

In .ASPX File
asp:TemplateColumn HeaderText="ContactName"
ItemTemplate
asp:Label id="Label2" runat="server" Text='%#

GetEmailLink(DataBinder.Eval(Container.DataItem,"ContactName"),DataBinder.Eval(Container.Dat

aItem,"Email")) %'lblCompanyName/asp:Label
/ItemTemplate
/asp:TemplateColumn

In .CS File
public static string GetEmailLink(object DisplayText,object EmailAddress)
{
return "a href='mailto:" + EmailAddress.ToString() + "'" + DisplayText.ToString() +

"/a";
}





Example3: Opening a Pop-up Link on clicking datagrid column.

In .ASPX File
asp:TemplateColumn HeaderText="Contact"
ItemTemplate
asp:Label id="Label2" runat="server" Text='%#

OpenPopupLink(DataBinder.Eval(Container.DataItem,"ContactName"),DataBinder.Eval(Container.Da

taItem,"CustomerId")) %'lblContactName/asp:Label
/ItemTemplate
/asp:TemplateColumn

In .CS File
public static string OpenPopupLink(object displayText,object displayId)
{
return "a href='http:Webform2.aspx?NameField=" + displayId.ToString() + "'" +

displayText.ToString() + "/a";
}





Example4: Displaying no. of characters to be displayed for a particular datagrid column.
Here displaying 5 characters.

In .ASPX File
asp:TemplateColumn HeaderText="Address"
ItemTemplate
asp:Label id="Label1" runat="server" Text='%#

GetFormatedText(ConcatColumns(DataBinder.Eval(Container.DataItem,"City"),DataBinder.Eval(Con

tainer.DataItem,"Country")),5) %'lblCompanyName/asp:Label
/ItemTemplate
/asp:TemplateColumn

In .CS File
public static string GetFormatedText(object objText, object objChars)
{
if (objText.ToString().Length int.Parse(objChars.ToString()))
return objText.ToString().Substring(0, int.Parse(objChars.ToString()));
else
return objText.ToString();
}



Example5: Displaying Calculation, Calculating UnitPrice into Quantity and displaying Total

In .ASPX File
asp:TemplateField HeaderText="Total"
EditItemTemplate
asp:TextBox ID="TextBox1" runat="server"/asp:TextBox
/EditItemTemplate
ItemTemplate
asp:Label ID="Label1" runat="server" Text='%#

CalculateTotal(DataBinder.Eval(Container.DataItem,"UnitPrice"),DataBinder.Eval(Container.Dat

aItem,"Quantity")) %'/asp:Label
/ItemTemplate
/asp:TemplateField

In .CS File
public static string CalculateTotal(object UnitPrice, object Quantity)
{
double Total = double.Parse(UnitPrice.ToString()) * long.Parse(Quantity.ToString());
return Total.ToString();
}





Example6: Applying conditional formatting to datagrid cell, assigning different colors to cell depends on its InputValue.

In .ASPX File
asp:TemplateField HeaderText="Total"
EditItemTemplate
asp:TextBox ID="TextBox1" runat="server"/asp:TextBox
/EditItemTemplate
ItemTemplate
asp:Label ID="Label1" runat="server" Text='%#

CalculateTotal(DataBinder.Eval(Container.DataItem,"UnitPrice"),DataBinder.Eval(Container.Dat

aItem,"Quantity")) %' ForeColor='%#

ConditionalFormating(CalculateTotal(DataBinder.Eval(Container.DataItem,"UnitPrice"),DataBind

er.Eval(Container.DataItem,"Quantity"))) %'/asp:Label
/ItemTemplate
/asp:TemplateField

In .CS File
public static Color ConditionalFormating(object Amount)
{
double dAmount = double.Parse(Amount.ToString());
if (dAmount 1000)
{
return Color.Red;
}
else if (dAmount 500)
{
return Color.Blue;
}
else
{
return Color.Green;
}
}



However, using this method does impose a performance penalty on your code because all the work it does is late-bound.

11 comments:

Anonymous said...

You can find more on Databinder.Eval Method() : http://weblogs.asp.net/rajbk/archive/2004/07/20/188868.aspx

DotNetGuts said...

DataBinder.Eval Method on MSDN, http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/frlrfSystemWebUIDataBinderClassEvalTopic.asp

divya said...

Thanks, it had help me

aditi said...

Nice Article, Thanks

aditi said...

Nice Article, Thanks

Pappu said...

Thanks a lot... Wonderful article...

sujith said...

Excellent article...

Rony said...

Just what that I was looking for.
Thank you. :-)

Anonymous said...

Thanks. Excellent article.

Anonymous said...

nice link

Anonymous said...

thanks for the nice article its helped a lot to me

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