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copied!<p>Is this what you're looking for? There are two flavors of the method: the first lets you pass in the new input type as an argument; the second lets you pass in the input type as a generic parameter and get a strongly typed LambdaExpression.</p> <pre><code> public static LambdaExpression ChangeInputType<T, TResult>(Expression<Func<T, TResult>> expression, Type newInputType) { if (!typeof(T).IsAssignableFrom(newInputType)) throw new Exception(string.Format("{0} is not assignable from {1}.", typeof(T), newInputType)); var beforeParameter = expression.Parameters.Single(); var afterParameter = Expression.Parameter(newInputType, beforeParameter.Name); var visitor = new SubstitutionExpressionVisitor(beforeParameter, afterParameter); return Expression.Lambda(visitor.Visit(expression.Body), afterParameter); } public static Expression<Func<T2, TResult>> ChangeInputType<T1, T2, TResult>(Expression<Func<T1, TResult>> expression) { if (!typeof(T1).IsAssignableFrom(typeof(T2))) throw new Exception(string.Format("{0} is not assignable from {1}.", typeof(T1), typeof(T2))); var beforeParameter = expression.Parameters.Single(); var afterParameter = Expression.Parameter(typeof(T2), beforeParameter.Name); var visitor = new SubstitutionExpressionVisitor(beforeParameter, afterParameter); return Expression.Lambda<Func<T2, TResult>>(visitor.Visit(expression.Body), afterParameter); } public class SubstitutionExpressionVisitor : ExpressionVisitor { private Expression before, after; public SubstitutionExpressionVisitor(Expression before, Expression after) { this.before = before; this.after = after; } public override Expression Visit(Expression node) { return node == before ? after : base.Visit(node); } } </code></pre>

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