stride3d/stride · error · ArgumentNullException

paramKey

Error message

paramKey

What it means

GetParam<T> throws ArgumentNullException("paramKey") when the PermutationParameterKey<T> used to look up a shader permutation parameter is null. The key is required to compute the global, composition, and selected keys for the lookup. Fail-fast guard before any parameter resolution happens.

Solutions

1. Pass a valid PermutationParameterKey<T> instance (e.g. MyShader.Permutation.PositionInput)
2. Verify the key exists in the shader's permutation keys after version changes
3. Add a null check before calling GetParam

Example fix

// before
var value = context.GetParam(FindKey(name)); // FindKey may return null
// after
var key = FindKey(name);
if (key != null) { var value = context.GetParam(key); }

if (paramKey is null) throw new InvalidOperationException("Permutation key not found");
var value = context.GetParam(paramKey);

static bool IsValidKey<T>(PermutationParameterKey<T> k) => k != null;

try { var value = context.GetParam(key); }
catch (ArgumentNullException) { throw new InvalidOperationException($"Unknown permutation key '{name}'"); }

When it happens

Trigger: Calling ctx.GetParam<T>(null) — usually when the key was retrieved from a dictionary/registry that lacked the entry and the null result was passed directly.

Common situations: Referencing a permutation key by string name that doesn't exist; keys defined in a different shader version no longer present after an upgrade.

Related errors

• key
• mixinTree
• compilerParameters
• registeredBuilders
• Invalid null mixin name

AI-assisted analysis of stride3d/stride@96fad776d2 (2026-09-14). Data as JSON: /api/errors/f73f6044c3968e82. Report an issue: GitHub.

Appendix: source

Thrown at sources/shaders/Stride.Shaders.Effects/ShaderMixinContext.cs:100

            }
        }

        public void Discard()
        {
            throw new ShaderMixinDiscardException();
        }

        /// <summary>
        /// Gets a parameter value for the specified key.
        /// </summary>
        /// <typeparam name="T">Type of the parameter value</typeparam>
        /// <param name="paramKey">The parameter key.</param>
        /// <returns>The value or default value associated to this parameter key.</returns>
        /// <exception cref="System.ArgumentNullException">key</exception>
        public T GetParam<T>(PermutationParameterKey<T> paramKey)
        {
            if (paramKey == null)
                throw new ArgumentNullException("paramKey");

            var globalKey = paramKey;
            var composeKey = GetComposeKey(paramKey);
            var selectedKey = globalKey;
            ParameterCollection sourceParameters = null;

            // Try first if a composite key with a value is available for the key
            if (composeKey != globalKey)
            {
                sourceParameters = FindKeyValue(composeKey, out selectedKey);
            }

            // Else try using global key
            if (sourceParameters == null)
            {
                sourceParameters = FindKeyValue(globalKey, out selectedKey);
            }

View on GitHub (pinned to 96fad776d2)