选择数组维度的高效代码实现咨询（附现有代码片段）

Hey there! Let's clean up that repetitive dimension selection code to make it more efficient and maintainable. Your original snippet has a lot of duplicated logic (like reinitializing the array and calling To3D in every branch) that we can eliminate with a cleaner approach.

First, Let's Spot the Pain Points #

• Redundant Code: You're initializing to3dimen twice per branch and calling To3D repeatedly—this is unnecessary and adds clutter.
• Scattered Values: Dimension values are hardcoded across multiple conditionals, making updates a hassle (you'd have to change them in 3 places if, say, the 4x8x8 dimension needs tweaking).
• Incomplete Logic: Your last branch cuts off, but we'll account for that in the optimized versions.

Optimized Approach 1: Use a Dictionary for Dimension Mapping #

This approach centralizes all your dimension mappings, so you can update values in one place and avoid repetitive setup:

private int[, ,] dim(int[] m) { 
    // Start with default dimensions (adjust these if you have a fallback case)
    int ww = 0, ll = 0, hh = 0;

    // Map each mm value to its corresponding (width, length, height) tuple
    var dimensionLookup = new Dictionary<int, (int w, int l, int h)>
    {
        { 1, (4, 8, 8) },
        { 4, (4, 8, 8) },
        { 7, (4, 8, 8) },
        { 2, (8, 4, 8) },
        { 5, (8, 4, 8) },
        { 8, (8, 4, 8) },
        { 3, (8, 8, /* add your missing hh value here */) },
        { 6, (8, 8, /* add your missing hh value here */) },
        { 9, (8, 8, /* add your missing hh value here */) }
    };

    // Grab the dimensions if mm is in our lookup table
    if (dimensionLookup.TryGetValue(mm, out var dims))
    {
        ww = dims.w;
        ll = dims.l;
        hh = dims.h;
    }

    // Initialize the array and populate it only if dimensions are valid
    int[, ,] to3dimen = new int[ww, ll, hh];
    if (ww > 0 && ll > 0 && hh > 0)
    {
        to3dimen = To3D(m, ww, ll, hh);
    }

    return to3dimen;
}

Optimized Approach 2: Switch Expression (C# 8.0+) #

If you prefer a more concise, readable approach, switch expressions are perfect here—they directly map mm values to dimensions without extra boilerplate:

private int[, ,] dim(int[] m) { 
    // Use a switch expression to get dimensions in one line
    (int ww, int ll, int hh) = mm switch
    {
        1 or 4 or 7 => (4, 8, 8),
        2 or 5 or 8 => (8, 4, 8),
        3 or 6 or 9 => (8, 8, /* fill in your missing hh value */),
        _ => (0, 0, 0) // Default case for unexpected mm values
    };

    // Set up the array and call To3D only if dimensions are valid
    int[, ,] to3dimen = new int[ww, ll, hh];
    if (ww != 0 && ll != 0 && hh != 0)
    {
        to3dimen = To3D(m, ww, ll, hh);
    }

    return to3dimen;
}

Why These Are Better #

• Less Repetition: No more copying the same array setup or To3D calls—all logic happens in one place.
• Easier to Maintain: If you need to update a dimension (e.g., change 4x8x8 to 4x16x8), you only modify one line instead of three.
• Safer: Both approaches handle unexpected mm values gracefully with default dimensions, and we only call To3D when we have valid non-zero dimensions.
• Scalable: Adding new mm values is as simple as adding a new entry to the dictionary or a new case in the switch expression.

内容的提问来源于stack exchange，提问作者Yussra