添加项目文件。

gong-wpf-dragdrop/src/GongSolutions.WPF.DragDrop/IDragSource.cs

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+using System;
+using System.Windows;
+
+namespace GongSolutions.Wpf.DragDrop
+{
+    /// <summary>
+    /// Interface implemented by Drag Handlers.
+    /// </summary>
+    public interface IDragSource
+    {
+        /// <summary>
+        /// Queries whether a drag can be started.
+        /// </summary>
+        /// 
+        /// <param name="dragInfo">
+        /// Information about the drag.
+        /// </param>
+        /// 
+        /// <remarks>
+        /// To allow a drag to be started, the <see cref="DragInfo.Effects"/> property on <paramref name="dragInfo"/> 
+        /// should be set to a value other than <see cref="DragDropEffects.None"/>. 
+        /// </remarks>
+        void StartDrag(IDragInfo dragInfo);
+
+        /// <summary>
+        /// With this action it's possible to check if the drag/drop operation is allowed to start
+        /// e.g. check for a UIElement inside a list view item, that should not start a drag/drop operation
+        /// </summary>
+        bool CanStartDrag(IDragInfo dragInfo);
+
+        /// <summary>
+        /// Notifies the drag handler that a drop has occurred.
+        /// </summary>
+        /// 
+        /// <param name="dropInfo">
+        ///   Information about the drop.
+        /// </param>
+        void Dropped(IDropInfo dropInfo);
+
+        /// <summary>
+        /// Notifies the drag handler that a drag and drop operation has finished.
+        /// </summary>
+        /// <param name="operationResult">The operation result.</param>
+        /// <param name="dragInfo">The drag information.</param>
+        void DragDropOperationFinished(DragDropEffects operationResult, IDragInfo dragInfo);
+
+        /// <summary>
+        /// Notifies the drag handler that a drag has been aborted.
+        /// </summary>
+        void DragCancelled();
+
+        /// <summary>
+        /// Notifies that an exception has occurred upon dragging.
+        /// </summary>
+        /// <param name="exception">
+        /// The exception that occurrred.
+        /// </param>
+        /// <returns>
+        /// Boolean indicating whether the exception is handled in the drag handler.
+        /// False will rethrow the exception.
+        /// </returns>
+        bool TryCatchOccurredException(Exception exception);
+    }
+}