dotnet/wpf · error · InvalidOperationException

SR.Format(SR.BindingConflict…

Error message

SR.Format(SR.BindingConflict, SourceProperties.StaticSource, _sourceInUse)

What it means

A WPF Binding may have only one source: Source, RelativeSource, ElementName, or (static compat path) SourceReference/StaticSource. Setting the static SourceReference (StaticSource) while _sourceInUse already records another source throws InvalidOperationException with SR.BindingConflict naming the conflicting properties.

Solutions

Set exactly one source property; clear others (Source = null, RelativeSource = null, ElementName = null) before assigning another.
Create a fresh Binding instance per element instead of mutating a shared one.
Use the modern StaticResource/MarkupExtension path rather than SourceReference on .NET 4.5+.

Example fix

// before
var b = new Binding { Source = obj };
b.SourceReference = StaticSourceRef; // conflict
// after
var b = new Binding { Source = obj }; // single source only

Defensive patterns

Strategy: try-catch

Validate before calling

static bool CanSetStaticSource(Binding b) =>
    b.Source == null && b.RelativeSource == null && string.IsNullOrEmpty(b.ElementName);

Try / catch

try { binding.SourceReference = staticRef; } catch (InvalidOperationException ex) when (ex.Message.Contains("conflict")) { binding = new Binding { SourceReference = staticRef }; }

Prevention

Assign exactly one of Source/RelativeSource/ElementName per Binding.
Never mutate shared Binding instances; create a new one per use.
When building bindings from merged definitions, sanitize source properties first.

When it happens

Trigger: In the Binding constructor/compat path: assigning a StaticSourceRef-based binding when Source, RelativeSource, or ElementName is already set (except under Desktop_V4_0 compat preferences).

Common situations: Constructing bindings in code that copy properties from XAML-defined bindings; shared/deferred Binding instances reused across elements; .NET 4.5 static-binding compat changes mixing with manually set Source.

Understand the failure class

Background: Conflicting config options: "cannot be used together" — configuration validation errors across open-source libraries — this error's family across 162 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/f8e530d515a74105. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Data/Binding.cs:317

            get { return _ppath; }
            set
            {
                CheckSealed();

                _ppath = value;
                _attachedPropertiesInPath = -1;
                ClearFlag(BindingFlags.PathGeneratedInternally);

                if (_ppath != null && _ppath.StartsWithStaticProperty)
                {
                    if (_sourceInUse == SourceProperties.None || _sourceInUse == SourceProperties.StaticSource ||
                        FrameworkCompatibilityPreferences.TargetsDesktop_V4_0) 
                    {
                        // net 4.5 breaks static bindings - this is for compat
                        SourceReference = StaticSourceRef;
                    }
                    else
                        throw new InvalidOperationException(SR.Format(SR.BindingConflict, SourceProperties.StaticSource, _sourceInUse));
                }
            }
        }

        /// <summary>
        /// This method is used by TypeDescriptor to determine if this property should
        /// be serialized.
        /// </summary>
        [EditorBrowsable(EditorBrowsableState.Never)]
        public bool ShouldSerializePath()
        {
            return _ppath != null && !TestFlag(BindingFlags.PathGeneratedInternally);
        }

        /// <summary> The XPath path (for XML bindings).</summary>
        [DefaultValue(null)]
        public string XPath
        {

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