Reputation: 51
Case/Switch Statements in C#
I wanted to know if there's a way to declare a lot of case statements without having to write all of them. For example, my code:
switch (Weight)
{
case 0 to 2;
ShippingCost = "3.69";
case 3 to 4;
ShippingCost = "4.86";
case 5 to 6;
ShippingCost = "5.63";
case 7 to 8;
ShippingCost = "5.98";
case 9 to 10;
ShippingCost = "6.28";
case 11 to 30;
ShippingCost = "15.72";
}
I started converting VB to C# and realized that in order to have more than one case statements you have to declare them. As you can see I have 11 to 30 and do not wanna have all those lines.
Upvotes: 1
Views: 823
Answers (10)
Reputation: 2061
I'd recommend storing the data in a container and iterating through the container. You could create your own class or use a .net class like Tuple:
var shippingCostsByWeight = new List<Tuple<int, int, string>>
{
new Tuple<int, int, string>(0, 2, "3.69"),
new Tuple<int, int, string>(3, 4, "4.86"),
new Tuple<int, int, string>(5, 6, "5.63"),
new Tuple<int, int, string>(7, 8, "5.98"),
new Tuple<int, int, string>(9, 10, "6.28"),
new Tuple<int, int, string>(11, 30, "15.72"),
};
ShippingCost = shippingCostsByWeight
.First(tuple => weight >= tuple.Item1 && weight <= tuple.Item2).Item3;
Upvotes: 0
Reputation: 109852
An alternative to using a case would be to write some kind of class to do the mapping, for example:
public sealed class CostsPerWeight
{
class CostPerWeight
{
public int Low;
public int High;
public double Cost;
}
readonly List<CostPerWeight> costs = new List<CostPerWeight>();
public CostsPerWeight Add(int low, int high, double result)
{
// Error handling omitted for brevity.
// Real code should check that low < high and that ranges do not overlap.
costs.Add(new CostPerWeight { Low = low, High = high, Cost = result } );
return this;
}
public double Cost(int weight)
{
// This throws if the weight isn't in the list.
// If that's not what you want, you'd have to add extra error handling here.
return costs.First(x => x.Low <= weight && weight <= x.High).Cost;
}
}
Which you would use like this (I've used doubles instead of strings for the costs for this example, but you can use whatever type you need):
var costs = new CostsPerWeight()
.Add( 0, 2, 3.69)
.Add( 3, 4, 4.86)
.Add( 5, 6, 5.63)
.Add( 7, 8, 5.98)
.Add( 9, 10, 6.28)
.Add(11, 30, 15.72);
double shippingCost = costs.Cost(weight);
If you have a lot of these switch statements in VB, it would be worth considering this approach.
(The advantage of using this instead of a Linq one-liner is simply that it's easier to document and unit test. You could also create a CostsPerWeight class instance and pass it around - useful for decoupling code, dependency-injection and for unit testing.)
It does seem to me that the concept of looking up a cost based on a weight is crying out to be encapsulated in a class, rather than embedded piecemeal in various parts of the code.
Here's a more extended example of CostsPerWeight with more error handling:
public class CostsPerWeight
{
class CostPerWeight
{
public int Low;
public int High;
public double Cost;
}
readonly List<CostPerWeight> costs = new List<CostPerWeight>();
double min = double.MaxValue;
double max = double.MinValue;
double costForMin;
public CostsPerWeight Add(int low, int high, double cost)
{
if (low > high)
throw new ArgumentException(nameof(low) + " must be less than " + nameof(high));
if (cost < 0)
throw new ArgumentOutOfRangeException(nameof(cost), "cost must be greater than zero");
costs.Add(new CostPerWeight { Low = low, High = high, Cost = cost } );
if (low < min)
{
min = low;
costForMin = cost;
}
if (high > max)
max = high;
return this;
}
public double Cost(int weight)
{
if (weight < min)
return costForMin;
if (weight > max)
throw new InvalidOperationException($"Weight {weight} is out of range: Must be <= {max}");
return costs.First(x => x.Low <= weight && weight <= x.High).Cost;
}
}
Upvotes: 3
Reputation:
The clearest way is to put your data into objects instead.
private struct ShippingCost
{
public int MinWeight;
public int MaxWeight;
public decimal Cost;
public ShippingCost(int min, int max, decimal cost)
{
MinWeight = min;
MaxWeight = max;
Cost = cost;
}
}
private List<ShippingCost> Costs = new List<ShippingCost>
{
new ShippingCost(0, 2, 3.69m),
new ShippingCost(3, 4, 4.86m),
new ShippingCost(5, 6, 5.63m),
new ShippingCost(7, 8, 5.98m),
new ShippingCost(9, 10, 6.28m),
new ShippingCost(11, 30, 15.72m),
};
// Choose shipping cost
public decimal CalcShippingCost(int weight)
{
foreach (ShippingCost sc in Costs)
{
if (weight >= sc.MinWeight && weight <= sc.MaxWeight)
return sc.Cost;
}
return 0.00m; // default cost
}
Upvotes: 3
Reputation: 5121
How bout just using this sort of approach
private static double GetShippingCost(double weight)
{
if (weight > 30) throw new ArgumentException("Weight over allowed maximum", "weight");
if (weight <= 2) return 3.69;
if (weight <= 4) return 4.86;
if (weight <= 6) return 5.63;
if (weight <= 8) return 5.98;
if (weight <= 10) return 6.28;
if (weight <= 30) return 15.72;
}
Upvotes: 4
Reputation: 2623
You cannot use comparisons in C# as you can in VB. You can however use fall-through cases, like so:
case 0:
case 1:
case 2:
ShippingCost = "3.69";
break;
case 3:
case 4:
ShippingCost = "4.86";
break;
Note that non-empty cases require either a throw, return or,break statement. Also note that you can only fall-through on empty cases.
Edit:
For completeness, as others have pointed out, it is probably more sensible in this case to use a series of if statements, like so:
if(Weight<=2) {
ShippingCost = "3.69";
}
else if(Weight <= 4) {
ShippingCost = "4.86";
}
... etc
Upvotes: 13
Reputation: 12854
There is direct equivalent in C#, however, you can use fall-through so you don't have to repeat the implementation:
switch (Weight)
{
case 0:
case 1:
case 2:
ShippingCost = "3.69";
break;
...
If statements would probably suit you much better in this scenario:
if(Weight >= 0 && Weight <= 2){
ShippingCost = "3.69";
} else if(Weight >= 3 && Weight <= 4){
ShippingCost = "4.86";
}
...
Upvotes: 6
Reputation: 121067
You could also write it as a Linq one liner:
var ShippingCost = (new[] { new { w = 2, p = "3,69" },
new { w = 4, p = "4.86" },
new { w = 6, p = "5.63" },
new { w = 8, p = "5.98" },
new { w = 10, p = "6.28" },
new { w = 30, p = "15.72" }})
.First(x => Weight <= x.w).p;
You would, as others have already stated, want to make sure that shipping for items weighing more than 30 is also handled correctly.
Upvotes: 5
Reputation: 68685
Try like this: This solutions removes the need to write && in your else if statements
if(Weight >= 11 && Weight <= 30)
{
ShippingCost = "15.72";
}
else if(Weight >= 9)
{
ShippingCost = "6.28";
}
else if(Weight >= 7)
{
ShippingCost = "5.98";
}
else if(Weight >= 5)
{
ShippingCost = "5.63";
}
else if(Weight >= 3)
{
ShippingCost = "4.86";
}
else if(Weight >= 0)
{
ShippingCost = "3.69";
}
Upvotes: 5
Reputation: 21
You could use a fall-through case switch statement, which goes as the following:
case 0:
case 1:
case 2:
shippingCost = "3.69";
break;
... and so on
Which will cause 0 to set shippingCost to 3.69 aswell as 1 and 2. :)
That would be my Solution to this
Upvotes: -1
Reputation: 187
You can't do that in C#. The best option if your max value for weight is 30 is to the use the default case.
Otherwise, if you don't want something like
case 11:
case 12:
case 13:
....
case 28:
case 29:
case 30:
an "oldschool" if/else if will be the the most readable solution
Upvotes: 1