title: How to change Parameters Expression to Constant Expression in Binary Expression
body: <p>I have my custom Visitor which looks to right and left and changes parameters  to constant.
  <br>
  I know that just change node is not possible.
  <br>
  I should return new lambda expression which contains constants instead parameters. 
  But I can not create an expression myself :(
  <br>
  I have this code:</p>
  
  <pre><code>    public class ParametersTransformToConstantVisitor : ExpressionVisitor
      {
  
      private Dictionary&lt;string, ConstantExpression&gt; parameters = new Dictionary&lt;string, ConstantExpression&gt;();
  
      public ParametersTransformToConstantVisitor(Dictionary&lt;string, ConstantExpression&gt; parameters)
      {
          this.parameters = parameters;
      }
  
      protected override Expression VisitBinary(BinaryExpression node)
      {
          var constExprLeftName = new Lazy&lt;string&gt;(() =&gt; ((ParameterExpression) node.Left)?.Name);
          var constExprRightName = new Lazy&lt;string&gt;(() =&gt; ((ParameterExpression) node.Right)?.Name);
          var constExprName = new Lazy&lt;string&gt;(() =&gt; ((ParameterExpression) node.Reduce())?.Name);
  
          ParameterExpression leftParam = null;
          ParameterExpression rightParam = null;
  
          if (node.NodeType == ExpressionType.Parameter &amp;&amp; parameters.ContainsKey(constExprName.Value))
          {
              return parameters[constExprName.Value];
          }
  
          if (node.Left.NodeType == ExpressionType.Parameter &amp;&amp; parameters.ContainsKey(constExprLeftName.Value))
          {
              leftParam = (ParameterExpression) node.Left;
          }       
  
          if (node.Right.NodeType == ExpressionType.Parameter &amp;&amp; parameters.ContainsKey(constExprLeftName.Value))
          {
              rightParam = (ParameterExpression) node.Right;
          }
  
          if (leftParam != null || rightParam != null)
          {
              //return Expression.Lambda();
          }       
  
          return base.VisitBinary(node);
      }
  }
  </code></pre>
  
  <p>Help me to build lambda expression, please</p>