Multiple conditions for same table in EF

Question

I am getting products using given parameters (name of real entity and columns changed for illustration purposes),

 public IQueryable<Product> GetProductsByPara(string price, string weight, string dimensions, string trend)
 {
 var result = dbContext.Products.Where(a =>
 a.Price.ToLower().Equals(price.ToLower()) && 
 a.Weight.ToLower().Equals(weight.ToLower()) &&
 a.Dimensions.ToLower().Equals(dimensions.ToLower()) &&
 a.Trend.ToLower().Equals(trend.ToLower()));
 if (result.Any())
 {
 return result;
 }
 if (!string.IsNullOrWhiteSpace(price))
 {
 result = dbContext.Products.Where(a =>
 a.Price.ToLower().Equals(price.ToLower()) && 
 a.Weight.ToLower().Equals(weight.ToLower()) &&
 a.Trend.ToLower().Equals(trend.ToLower()));
 if (result.Any())
 {
 return result;
 }
 }
 if (!string.IsNullOrEmpty(dimensions))
 {
 result = dbContext.Products.Where(a =>
 a.Dimensions.ToLower().Equals(dimensions.ToLower()) &&
 a.Weight.ToLower().Equals(weight.ToLower()) &&
 a.Trend.ToLower().Equals(trend.ToLower()));
 if (result.Any())
 {
 return result;
 }
 }
 return result;
 }

• BCdotWEB: Why are price and weight strings? That makes no sense.
• Mathematics: @BCdotWEB As mentioned in question, names are changed for illustration purposes. thanks

Answer 1

Here is an approach to get rid of some of the redundancy:

First write an extension Method

static IQueryable<Product> FilterForParameters
 (this IQueryable<Product> query, string price, string weight, string dimensions, string trend)
{
 if (price != null)
 query = query.Where(p => p.Price.ToLower().Equals(price.ToLower()));
 if (weight != null)
 query = query.Where(p => p.Weight.ToLower().Equals(weight.ToLower()));
 if (dimensions != null)
 query = query.Where(p => p.Dimension.ToLower().Equals(dimensions.ToLower()));
 if (trend != null)
 query = query.Where(p => p.Trend.ToLower().Equals(trend.ToLower()));
 return query;
}

Then change your method

public IQueryable<Product> GetProductsByPara(string price, string weight, string dimensions, string trend)
{
 var products = dbContext.Products;
 var productsFilterdByAll = products.FilterForParameters(price, weight, dimensions, trend);
 if (productsFilterdByAll.Any())
 return productsFilterdByAll;
 var productsFilterdByAllButDimnensions = products.FilterForParameters(price, weight, null, trend);
 if (productsFilterdByAllButDimnensions.Any())
 return productsFilterdByAllButDimnensions;
 var productsFilterdByAllButPrice = products.FilterForParameters(null, weight, dimensions, trend);
 return productsFilterdByAllButPrice;
}

Depending on the context, it would also be a good idea to check your parameters for null at the beginning of the method.

Answer 2

use ternary operator as condition ? true : false;

public IQueryable<Product> GetProductsByPara(string price, string weight, string dimensions, string trend)
{
 return dbContext.Products.Where(a =>
 a.Price.Equals(!string.IsNullOrEmpty(dimensions) ? a.Price : price,StringComparison.OrdinalIgnoreCase) 
 && a.Weight.Equals(weight, StringComparison.OrdinalIgnoreCase) 
 && a.Dimensions.Equals(!string.IsNullOrWhiteSpace(price) ? a.Dimensions : dimensions, StringComparison.OrdinalIgnoreCase) 
 && a.Trend.Equals(trend, StringComparison.OrdinalIgnoreCase) 
 );
}

It is unnecessary to repeat:

if (result.Any())
{
 return result;
}

.

Also, using StringComparison.OrdinalIgnoreCase would be much more appropriate than ToLower()

• Tim Pohlmann: OP is changing the content of result. So checking for result.Any() multiple times is actually a reasonable thing to do.