TheAlgorithms/C-Sharp · error · ArgumentException

Minimum degree must be at least 2.

Error message

Minimum degree must be at least 2.

What it means

This ArgumentException is thrown by the BTree(int minimumDegree = 2) constructor when a minimum degree below 2 is passed. A B-tree requires a minimum degree of at least 2 (each node must be able to hold at least 1 key and have at least 2 children); any lower value makes the tree's split/merge invariants mathematically impossible. The parameter name is included in the exception, pointing directly at the invalid argument.

Solutions

1. Pass a minimumDegree value of at least 2; use the parameterless constructor (default 2) if unsure.
2. Clamp or validate the incoming value before constructing: if (degree < 2) degree = 2; or throw your own descriptive error.
3. If the degree comes from configuration, add a config validation step enforcing minimumDegree >= 2 with a clear message.
4. Double-check terminology: minimum degree t means each non-root node has at least t-1 keys and t children.

Example fix

// before
var tree = new BTree<int>(1); // ArgumentException

// after
int degree = Math.Max(2, configuredDegree);
var tree = new BTree<int>(degree);

// C#
if (minimumDegree < 2)
    throw new ArgumentOutOfRangeException(nameof(minimumDegree),
        "B-Tree minimum degree must be at least 2.");
var tree = new BTree<TKey>(minimumDegree);

// C#
BTree<TKey> tree;
try
{
    tree = new BTree<TKey>(minimumDegree);
}
catch (ArgumentException ex)
{
    // fall back to default degree
    tree = new BTree<TKey>();
}

When it happens

Trigger: Invoking new BTree<TKey>(minimumDegree) with minimumDegree of 1, 0, or a negative number — e.g. a computed/default-derived value that is 0 or 1, or passing 1 believing it means 'one-key nodes'. The parameterless form (default 2) never throws.

Common situations: Reading the degree from configuration where a default of 0 leaks through; an off-by-one assumption that minimum degree counts keys rather than children; arithmetic like degree = branchingFactor - 1 producing 1 when branchingFactor is 2.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

• k must be at least 1.
• Key " " is not in the B-Tree.
• B-Tree is empty.
• Capacity must be greater than 0
• Load factor must be greater than 0

AI-assisted analysis of TheAlgorithms/C-Sharp@96e2905cab (2026-09-13). Data as JSON: /api/errors/8ebf7275797482fc. Report an issue: GitHub.

Appendix: source

Thrown at DataStructures/BTree/BTree.cs:70

    /// </summary>
    private BTreeNode<TKey>? root;

    /// <summary>
    ///     Initializes a new instance of the <see cref="BTree{TKey}"/>
    ///     class with the specified minimum degree.
    /// </summary>
    /// <param name="minimumDegree">
    ///     Minimum degree (t) of the B-Tree. Must be at least 2.
    ///     Each node can contain at most 2t-1 keys.
    /// </param>
    /// <exception cref="ArgumentException">
    ///     Thrown when minimumDegree is less than 2.
    /// </exception>
    public BTree(int minimumDegree = 2)
    {
        if (minimumDegree < 2)
        {
            throw new ArgumentException("Minimum degree must be at least 2.", nameof(minimumDegree));
        }

        MinimumDegree = minimumDegree;
        comparer = Comparer<TKey>.Default;
    }

    /// <summary>
    ///     Initializes a new instance of the <see cref="BTree{TKey}"/>
    ///     class with the specified minimum degree and custom comparer.
    /// </summary>
    /// <param name="minimumDegree">
    ///     Minimum degree (t) of the B-Tree. Must be at least 2.
    /// </param>
    /// <param name="customComparer">
    ///     Comparer to use when comparing keys.
    /// </param>
    /// <exception cref="ArgumentException">
    ///     Thrown when minimumDegree is less than 2.

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