IF...THEN in asp.net datagrid code

j45mw

Does anyone know how to create an IF...THEN statement in the ASP.NET datagrid HTML code. Within the code that creates the datagrid I need to display data in a cell IF a certain condition is met. And that is where the IF THEN comes in to play. I realize I could do this in Code Behind but I need to do it within the HTML code in order to allow an HTML designer to work with it also.

Mircea Grelus

Well, ASP.Net is serverside code which means code behind, so no, you cannot add ASP.NET in the html code. What I think you can do is bind all the data to the datagrid and on the client side execute a Javascript function that will hide or display the rows of the datagrid using style="display: none" to hide or style="display:''" to show. regards, Mircea Many people spend their life going to sleep when they’re not sleepy and waking up while they still are.

Mike Ellison

Just to offer another suggestion - you could use the C# ternary operator (condition ? valueIfTrue : valueIfFalse) within a databinding expression in a TemplateColumn to mimick an IF/THEN/ELSE evaluation. Here's an example; look at how the asp:TemplateColumn is defined to see what I mean.

<%@ Page Language="C#" %>
<%@ Import Namespace="System.Data" %>

// upon page load, initialize the grid
void Page\_Load(object o, EventArgs e)
{
    if (!IsPostBack)
    {
        myGrid.DataSource = CreateDataSource();
        myGrid.DataBind();            
    }
}

// Create the sample datasource for this exercise
private DataTable CreateDataSource()
{
    DataTable t = new DataTable();
    
    // create the table structure
    DataColumn c = new DataColumn();
    c.DataType = System.Type.GetType("System.Int32");
    c.ColumnName = "ID";
    c.Unique = true;
    t.Columns.Add(c);
    
    c = new DataColumn();
    c.DataType = System.Type.GetType("System.String");
    c.ColumnName = "Name";
    t.Columns.Add(c);        
    
    c = new DataColumn();
    c.DataType = System.Type.GetType("System.String");
    c.ColumnName = "City";
    t.Columns.Add(c);    
    
    // establish ID as the primary key
    DataColumn\[\] primaryKey = new DataColumn\[1\];
    primaryKey\[0\] = t.Columns\["ID"\];
    t.PrimaryKey = primaryKey;

    // populate the table with some sample rows of data
    DataRow r = t.NewRow();
    r\["id"\] = 1001;
    r\["Name"\] = "Jack Bauer";
    r\["City"\] = "Los Angeles";
    t.Rows.Add(r);
    
    r = t.NewRow();
    r\["id"\] = 1002;
    r\["Name"\] = "David Palmer";
    r\["City"\] = "Washington D.C.";
    t.Rows.Add(r);
    
    r = t.NewRow();
    r\["id"\] = 1003;
    r\["Name"\] = "Nina Meyers";
    r\["City"\] = "Los Angeles";
    t.Rows.Add(r);

    r = t.NewRow();
    r\["id"\] = 1004;
    r\["Name"\] = "Bill Buchanan";
    r\["City"\] = "Los Angeles";
    t.Rows.Add(r);
    
    return t;
}

</script>

<html>
<head>
<title>Conditional Output in a DataGrid</title>
<style> body {font-family: 'Tahoma'; font-size: 10pt;}</style>
</head>

<bo

munklefish

Mike, Could you explain what exactrly is going on here please, as this is something i think this code would be useful to a lot of people including myself.

Mike Ellison wrote:

<%# (DataBinder.Eval(Container.DataItem, "City") != "Washington D.C." ? "" : "Washington D.C." ) %>

Thanks!

Mike Ellison

Okay - first, the C# ternary operator follows this syntax: _condition_ ? _valueIfTrue_ : _valueIfFalse_ It allows for assignment expressions like the following example:

string sMessage = (sName == null ? "Name doesn't exist" : sName);

The above will test if sName is null; if it is, the variable sMessage is assigned the value "Name doesn't exist". If sName is not null, then sMessage is assigned the value sName. Now, the ternary operator may be applied within the context of a databinding expression, as in this excerpt from the example I posted earlier:

<%# (DataBinder.Eval(Container.DataItem, "City") != "Washington D.C." ? "" : "Washington D.C." ) %>

The condition in this example is DataBinder.Eval(Container.DataItem, "City") != "Washington D.C.". This uses the reflective DataBinder.Eval statement to evaluate the "City" field for a particular data row during binding. (Note: in ASP.NET 2.0, the shorthand Eval("City") could be used instead.) So the condition being evaluated in this example is whether or not the "City" field contains the value "Washington D.C.". If it contains something other than "Washington D.C." (the condition is using the not equals != operator), then the valueIfTrue element from the ternary operator is returned - in this case, a blank string "". If the condition is false (i.e. if the value is "Washington D.C.") then the valueIfFalse element from the ternary operator is returned - in this case, the literal text "Washington D.C.". My example would have been a bit cleaner if I had used an equality condition == rather than a not-equals condition != - sorry about that. Hopefully you understand what I'm getting at though.

munklefish

Mike, I understood the != part, it was more a case of what the subsequent bits were referring to and doing. However the explanation was excellent and cleared things up. Quick question for you thought. Is it possible to return the actual field value, rather than a specific string. Say for example you do the == to check for a given value. If this given value is not met then you just display the contents of the field, rather than having to actually tell it what string to display?

Mike Ellison

Sure - it's all in the context of one databinding expression, so anything that can be parsed/interpreted in that context is fair game. Here's an example - I'll use the ASP.NET 2.0 syntax, but you can expand it to the full DataBinder.Eval syntax if you want to:

<%# Eval("Discount") == 0 ? "No Discount" : Eval("Discount") %>

munklefish

Your Great! :-O:-O:-O:-O

munklefish

Mike, I tried the code as suggested, using the following in a DataList: <%# DataBinder.Eval("menuVegetarian") == 1 ? "wibble" : "poop" %> But i get the following error: CS1501: No overload for method 'Eval' takes '1' arguments So i added the Container part that ive used for all my other data displayed in the dataList. <%# DataBinder.Eval(Container, "menuVegetarian") == 1 ? "wibble" : "poop" %> But i get this error: CS0019: Operator '==' cannot be applied to operands of type 'object' and 'int' The value i'm comparing is stored as a Yes/No in Access 2003. So i tried doing it this way: <%# Convert.ToInt16(DataBinder.Eval(Container, "menuVegetarian")) == 1 ? "wibble" : "poop" %> Which gives the following error: DataBinder.Eval: 'System.Web.UI.WebControls.DataListItem' does not contain a property with the name menuVegetarian. Any ideas mate? Thanks Its not my fault im stoopid! :confused: -- modified at 7:22 Saturday 25th February, 2006 Got It: <%# Convert.ToInt16(DataBinder.Eval(Container, "DataItem.menuVegetarian")) == 1 ? "wibble" : "poop" %>

Mike Ellison

munklefish wrote:

Got It: <%# Convert.ToInt16(DataBinder.Eval(Container, "DataItem.menuVegetarian")) == 1 ? "wibble" : "poop" %>

Yup. DataBinder.Eval is looking at the object that is passed in the first argument, to evaluate its property (identified through the second string argument). You could also have done something like this I think:

<%# DataBinder.Eval(Container.DataItem, "menuVegetarian") == 1 ? "wibble" : "poop" %>

You might have had to use the Convert.ToInt16 code or not, it just depends on the field type itself.