A DSL For Significant Numbers

1.originalcode.cs

private AddAssetResult HandleAssetFamily(SortContainer container, SystemAsset systemAsset)
{
    AddAssetResult result = null;
    var assetFamilies = assetFamilyDao.GetByAssetType(systemAsset.AssetTypeId);

    if (assetFamilies == null || assetFamilies.Count == 0)
    {
        result = new AddAssetResult(SortContainerResources.NoAssetFamily);
    }

    if (assetFamilies != null && assetFamilies.Count > 1)
    {
        result = new AddAssetResult(SortContainerResources.MultipleAssetFamilies);
    }

    if (assetFamilies != null && assetFamilies.Count == 1)
    {
        var assetFamily = assetFamilies[0];
        SetContainerFamily(container, assetFamily);

        result = VerifyFamilyIsCompatible(systemAsset, container);
    }

    return result;
}

2.newcode.cs

private AddAssetResult HandleAssetFamily(SortContainer container, SystemAsset systemAsset)
{
    var assetFamilies = assetFamilyDao.GetByAssetType(systemAsset.AssetTypeId);

    var result = assetFamilies.CheckCount<AssetFamily, AddAssetResult>()
        .WhenZero(() => new AddAssetResult(SortContainerResources.NoAssetFamily))
        .WhenOne(() => AddAssetWithFamily(systemAsset, container, assetFamilies[0]))
        .WhenMany(() => new AddAssetResult(SortContainerResources.MultipleAssetFamilies))
        .Result;

    return result;
}

3.countchecker.cs

public static class CountCheckerExtensions
{
    public static CountChecker<TResult> CheckCount<TCollectionType, TResult>(this IEnumerable<TCollectionType> enumerable)
    {
        int theCount = 0;
        if (enumerable != null)
            theCount = enumerable.Count();
        return new CountChecker<TResult>(theCount);
    }
}

public class CountChecker<TResult>
{
    private readonly int theCount;

    public TResult Result { get; private set; }

    public CountChecker(int theCount)
    {
        this.theCount = theCount;
    }

    public CountChecker<TResult> WhenZero(Func<TResult> zeroAction)
    {
        if (theCount == 0)
            Result = zeroAction();

        return this;
    }

    public CountChecker<TResult> WhenOne(Func<TResult> oneAction)
    {
        if (theCount == 1)
            Result = oneAction();

        return this;
    }
    
    public CountChecker<TResult> WhenMany(Func<TResult> manyAction)
    {
        if (theCount > 1)
            Result = manyAction();

        return this;
    }
}