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copied!<p>I'm adding an expression based form as well. Do note the horrendous boxing/unboxing which needs to be done due to the fact that it is a struct. </p> <p>But as one can see the format is quite nice:</p> <pre><code>var p2 = p.With(t => t.X, 4); var p3 = p.With(t => t.Y, 7).With(t => t.X, 5); // Yeah, replace all the values :) </code></pre> <p>And the method is really applicable to all kinds of types.</p> <pre><code>public void Test() { var p = new Position(8, 3); var p2 = p.With(t => t.X, 4); var p3 = p.With(t => t.Y, 7).With(t => t.X, 5); Console.WriteLine(p); Console.WriteLine(p2); Console.WriteLine(p3); } public struct Position { public Position(int X, int Y) { this._X = X; this._Y = Y; } private int _X; private int _Y; public int X { get { return _X; } private set { _X = value; } } public int Y { get { return _Y; } private set { _Y = value; } } public Position With<T, P>(Expression<Func<Position, P>> propertyExpression, T value) { // Copy this var copy = (Position)this.MemberwiseClone(); // Get the expression, might be both MemberExpression and UnaryExpression var memExpr = propertyExpression.Body as MemberExpression ?? ((UnaryExpression)propertyExpression.Body).Operand as MemberExpression; if (memExpr == null) throw new Exception("Empty expression!"); // Get the propertyinfo, we need this one to set the value var propInfo = memExpr.Member as PropertyInfo; if (propInfo == null) throw new Exception("Not a valid expression!"); // Set the value via boxing and unboxing (mutable structs are evil :) ) object copyObj = copy; propInfo.SetValue(copyObj, value); // Since struct are passed by value we must box it copy = (Position)copyObj; // Return the copy return copy; } public override string ToString() { return string.Format("X:{0,4} Y:{1,4}", this.X, this.Y); } } </code></pre>

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