artgor

private static Array Combine(params object[] arrays)
        {
            if (arrays.Length == 0) return null;
            if (arrays.Length == 1) return (Array)arrays[0];

            var totalLength = ((Array)arrays[0]).Length;
            var elemType = arrays[0].GetType().GetElementType();
            for (int i = 1; i < arrays.Length; i++)
            {
                var nextElemType = arrays[i].GetType().GetElementType();
                if (nextElemType != elemType) return null;
                totalLength += ((Array)arrays[i]).Length;
            }
            
            Array resultArray = Array.CreateInstance(elemType, totalLength);

            var offset = 0;
            foreach (Array array in arrays)
            {
                Array.Copy(array, 0, resultArray, offset, array.Length);
                offset += array.Length;
            }

            return resultArray;
        }

static Array Combine(params object[] arr)
{
    if (arr.Length == 0)
    {
        return null;
    }

    var totalSize = 0;
    Type type = null;
    foreach (Array inner in arr)
    {
        var innerType = inner.GetType();
        type ??= innerType;

        if (innerType != type)
        {
            return null;
        }

        totalSize += inner.Length;
    }

    var resultArr = Array.CreateInstance(type.GetElementType(), totalSize);
    var currentSize = 0;

    foreach (Array inner in arr)
    {
        Array.Copy(inner, 0, resultArr, currentSize, inner.Length);
        currentSize += inner.Length;
    }

    return resultArr;
}