CODEWITHSUNDEEP
c#asp.netlinq
Kevin Verhoeven
Kevin Verhoeven

Reputation: 189

ASP.net LINQ: return items where id equals a variable

I use asp.net c# with webforms and I work with the dal+bll structure. This is my situation:

I have a starting page with 8 buttons, when I click on one of this buttons, I go to a page list.aspx.

On this page, there is data returned from the database with this LINQ code:

    var result = (from b in dc.Businesses
                  select b).ToList();
    return result;

This all works as it should. However, I want to make it so that if I click on button1, only the records with businessType "NighShop" are returned. When I click on button2, only records with idName "Bar" are returned etc. It would be stupid to make 8 different pages + DAL&BLL's for this.

So I figure the LINQ (in the DALBusiness.cs class layer) should be something like this:

    var result = (from b in dc.Businesses where b.BusinessType == aVariableValue
                  select b).ToList();
    return result;

And that variableValue can be altered whenever the user presses one of the 8 buttons. But I have no experience with this, so I don't know how to do this.

I tried to declare the var when I press on a button (on index page): 

public void Button1_Click(object sender, EventArgs e)
{
    var keuze = "Nachtwinkel";
}

But if I try:

public IList<Business> selectAll()
{
    var result = (from b in dc.Businesses where b.BusinessType == keuze
                  select b).ToList();
    return result;
}

On theDALBusiness.cs class layer, then it doesn't know the var keuze. I'm new to asp.net, so the answer might be really easy after all.

Upvotes: 1

Views: 3727

Answers (4)

MethodMan
MethodMan

Reputation: 18843

If it does not know that variable try making a method instead that compares to the anIdVariable will something like this work it's the same thing as the Linq but in more of a Method format just as an example

public bool FilterByBusinessTypeID(dc.Business dcBusiness)
{
   return dcBusiness.ID == anIdVariable;
}
var result= BusinessType.Where(FilterByBusinessTypeID).First();

Upvotes: 2

Couradical
Couradical

Reputation: 175

in the LINQ query it will evaluate references as typed. If you specify b.BusinessType == x and you have a type or entity "BusinessType", you will need to pass the object reference (i.e. x has to be typed "BusinessType"). You can get around this by doing something like the following: 

//this line in your OnClick function
keuze = "MyBusinessTypeName";

//this line in your data handler
var result = (from b in dc.Businesses where b.BusinessType.BusinessTypeName == keuze
              select b).ToList();

As Erix says, the keuze variable needs to be accessible to both. Hope that helps.

Upvotes: 2

Erix
Erix

Reputation: 7105

Try this. You need to store your Keuze value somewhere accessible to SelecAll().

public void Button1_Click(object sender, EventArgs e)
{
     Session["keuze"] = "Nachtwinkel";
}

public IList<Business> selectAll()
{
    var result = (from b in dc.Businesses where b.BusinessType == Session["keuze"]
                  select b).ToList();
    return result;
}

Upvotes: 3

twaggs
twaggs

Reputation: 3743

Are you meaning to just compare the Id's like:

var result = (from b in dc.Businesses where b.BusinessType.Id == anIdVariable
              select b).ToList();
return result;

Upvotes: 1

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