Can't build lambda expression tree

Trying to create the following expression using expression trees (would like help)

List<string> lstName = dt_Name.Select(y => y.Name);

List<string> lstLabName = dt_Label.Select(x => x.LabelName).Where(p => p.LabelName.StartsWith(lstName + '_'));

I would like it to actually go over all of lstName and find all the instances in lstLabName that meet the condition.

The code I came up with so far is:

    private BinaryExpression CreateBinaryExpression(string buildName)
    {
        // x.LabelName
        var param = Expression.Parameter(typeof(dt_Label), "x");
        var key = param.GetType().GetProperty("LabelName");
        var left = Expression.MakeMemberAccess(param, key);

        //ParameterExpression left = Expression.Parameter(typeof(string), "p"); //p
        ConstantExpression constantExpression = Expression.Constant(buildName, typeof(string));

        // x.LabelName == buildName
        return Expression.MakeBinary(ExpressionType.Equal, left, constantExpression);
    }

    private BinaryExpression CalculateLambdaExp(List<string> lstBuildName) 
    {
            BinaryExpression binaryExpression = CreateBinaryExpression(lstBuildName[0]);

            if (lstBuildName.Count() > 1)
            {
                List<string> lstnStr = lstBuildName;
                lstnStr.RemoveAt(0);
                BinaryExpression calculatedLambdaExp = CalculateLambdaExp(lstnStr);
                binaryExpression = Expression.MakeBinary(ExpressionType.AndAlso, binaryExpression, calculatedLambdaExp);
            }

            return binaryExpression;
    }

    private List<string> RunLambdaExpression(List<string> BuildName)
    {
        ParameterExpression left = Expression.Parameter(typeof(string), "p"); //p

        var factorial = Expression.Lambda<Func<List<string>, List<string>>>(CalculateLambdaExp(BuildName), left);
        var n = factorial.Compile()(BuildName);
        List<string> lst = n.ToList();

        return lst;
    }

I'm getting plenty of runtime errors. would appreciate any help.

figured most of it out:

changed the function CreateBinaryExpression to:

    private Expression CreateBinaryExpression(string buildName)
    {
        // x.LabelName
        var param = Expression.Parameter(typeof(dt_Label), "x");
        var key = typeof(dt_Label).GetProperty("LabelName");

        var left = Expression.MakeMemberAccess(param, key);

        ConstantExpression constantExpression = Expression.Constant(buildName + '_', typeof(string));

        //x.LabelName.startsWith(buildName_)
        MethodInfo mi = typeof(string).GetMethod("StartsWith", new Type[] { typeof(string) });
        Expression call = Expression.Call(left, mi, constantExpression);

        return call;
    };

and changed all references to the function to receive Expression instead of BinaryExpression