BlazorEditForms/Binding/ExpressionBuilder.cs

using System.Linq.Expressions;

namespace BlazorEditForms.Binding;

public static class ExpressionBuilder
{
    public static Expression<Func<TProperty>> CreateGetter<TProperty>(MemberExpression mex)
    {
        return Expression.Lambda<Func<TProperty>>(mex);
    }

    public static Expression<Action<TProperty>> CreateSetter<TProperty>(MemberExpression mex)
    {
        var valueParameter = Expression.Parameter(typeof(TProperty), "value");
        var assign = Expression.Assign(mex, valueParameter);
        return Expression.Lambda<Action<TProperty>>(assign, valueParameter);
    }

    public static Expression ReplaceParameter(Expression originalExpression, ParameterExpression parameter, Expression replacement)
    {
        return new ParameterReplacer(parameter, replacement).Visit(originalExpression);
    }

    /// <summary>
    /// This visitor replaces a specific function parameter with an actual value given as another
    /// expression.
    /// </summary>
    public class ParameterReplacer : ExpressionVisitor
    {
        private readonly ParameterExpression _parameter;
        private readonly Expression _replacement;

        public ParameterReplacer(ParameterExpression parameter, Expression replacement)
        {
            _parameter = parameter;
            _replacement = replacement;
        }

        protected override Expression VisitParameter(ParameterExpression node)
        {
            // Replace the parameter with the provided expression
            return node == _parameter ? _replacement : base.VisitParameter(node);
        }
    }
}