Question

i am using asp.net mvc3 and i am going to implement advance search
this is my advance search form

 @using (Html.BeginForm("AdvanceSearch","Coupon",FormMethod.Post))
    {
        @Html.ValidationSummary(true)
        <fieldset>

            <div class="editor-label">
                @Html.LabelFor(model => model.AdvanceSearch.CouponName)
            </div>
            <div class="editor-field">
                @Html.EditorFor(model => model.AdvanceSearch.CouponName)
                @Html.ValidationMessageFor(model => model.AdvanceSearch.CouponName)
            </div>

            <div class="editor-label">
                @Html.LabelFor(model => model.AdvanceSearch.Category)
            </div>
            <div class="editor-field">
                @Html.DropDownList("categories", new SelectList(Model.AdvanceSearch.Category.OrderBy(c=>c.Name).Select(c => c.Name)), "--- Select Categories ---")
                @Html.ValidationMessageFor(model => model.AdvanceSearch.Category)
            </div>
            <div class="editor-label">

                <div class="editor-label">
                    @Html.LabelFor(model => model.AdvanceSearch.CreateDate)
                </div>
                <div class="editor-field">
                    @Html.EditorFor(model => model.AdvanceSearch.CreateDate, new { @class = "picker" })
                    @Html.ValidationMessageFor(model => model.AdvanceSearch.CreateDate)
                </div>

                <div class="editor-label">
                    @Html.LabelFor(model => model.AdvanceSearch.ExpiredDate)
                </div>
                <div class="editor-field">
                    @Html.EditorFor(model => model.AdvanceSearch.ExpiredDate, new { @class = "picker" })
                    @Html.ValidationMessageFor(model => model.AdvanceSearch.ExpiredDate)
                </div>

                <div class="editor-label">
                    @Html.LabelFor(model => model.AdvanceSearch.PublishDate)
                </div>
                <div class="editor-field">
                    @Html.EditorFor(model => model.AdvanceSearch.PublishDate, new { @class = "picker" })
                    @Html.ValidationMessageFor(model => model.AdvanceSearch.PublishDate)
                </div>
                @Html.LabelFor(model => model.AdvanceSearch.Company)
            </div>
            <div class="editor-field">
                @Html.DropDownList("companies", new SelectList(Model.AdvanceSearch.Company.OrderBy(c=>c.Name).Select(c => c.Name)), "--- Select Companies ---")
                @Html.ValidationMessageFor(model => model.AdvanceSearch.Company)
            </div>
            <div class="editor-label">
                @Html.LabelFor(model => model.AdvanceSearch.Description)
            </div>
            <div class="editor-field">
                @Html.EditorFor(model => model.AdvanceSearch.Description)
                @Html.ValidationMessageFor(model => model.AdvanceSearch.Description)
            </div>

            <div class="editor-label">
                @Html.LabelFor(model => model.AdvanceSearch.IsPublish)
            </div>
            <div class="editor-field">
                @Html.EditorFor(model => model.AdvanceSearch.IsPublish)
                @Html.ValidationMessageFor(model => model.AdvanceSearch.IsPublish)
            </div>

            <div class="editor-label">
                @Html.LabelFor(model => model.AdvanceSearch.Active)
            </div>
            <div class="editor-field">
                @Html.EditorFor(model => model.AdvanceSearch.Active)
                @Html.ValidationMessageFor(model => model.AdvanceSearch.Active)
            </div>

            <p>
                <input type="submit" value="Search" />
            </p>
        </fieldset>
    }

now the problem is that i have following scenarios

• if only CouponName is given then all coupons contains specified name will be returned
• if any company is selected from company list then we will search all coupon from that company having specified name will be returned
• if any Category is selected from category list then we will search all coupon from that category having specified name will be returned
• if any date from all of threee date is been selected then we will filter coupon by that date

now i am confused that what is the best way to do that , should i implement if else conditions , switch or what ?

Answer 1

Not sure if there is a “best way”. It all depends on how you are applying the filter.

I use LINQ to apply filters and like to write my filter construction with a base expression, and then AND expressions for every provided filter selection. I use some extension methods to make this easier. Then you can build your filter expression in steps, and as it get more complex, you can implement steps accordingly. Each basic step would have a if check to see if a particular part was specified, and if it was append it to the base expression.

// Example of service for applying filter
public GetProductsResponse GetProducts(GetProductsRequest request)
{
    // base expression is true, ie always returns everything
    Expression<Func<ProductEntity, bool>> filterExpression = i => true;

    // subsequent filters narrow base expression results
    if (!request.IncludeDeleted)
        filterExpression = filterExpression.And(i => i
            .IsDeleted == false);

    // I like to use nullable types so that I can check whether a parameter is specified or not
    if (request.CouponName != null)
        filterExpression = filterExpression.And(i => 
            i.CouponName == request.CouponName.Value);

    if (request.Company!= null)
        filterExpression = filterExpression.And(i => 
            i.Company== request.Company.Value);

    // etc.

    var products = _dataContext.Products.Where(filterExpression);

    // you probably want to transform products into some sort of model specific class

    return new GetProductsRequest
    {
        products = products;
    };
}


// Extension methods for Linq And and Or helpers
public static class Utility
{
    public static Expression<T> Compose<T>(this Expression<T> first, Expression<T> second, Func<Expression, Expression, Expression> merge)
    {
        // build parameter map (from parameters of second to parameters of first)
        var map = first.Parameters.Select((f, i) => new { f, s = second.Parameters[i] }).ToDictionary(p => p.s, p => p.f);

        // replace parameters in the second lambda expression with parameters from the first
        var secondBody = ParameterRebinder.ReplaceParameters(map, second.Body);

        // apply composition of lambda expression bodies to parameters from the first expression 
        return Expression.Lambda<T>(merge(first.Body, secondBody), first.Parameters);
    }

    public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> first, Expression<Func<T, bool>> second)
    {
        return first.Compose(second, Expression.And);
    }

    public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> first, Expression<Func<T, bool>> second)
    {
        return first.Compose(second, Expression.Or);
    }
}