You can build an expression tree which contains a type conversion operation using Expression.Convert method. For example, you have the following code.
double val = 10.3;
Console.WriteLine((int)val);
Here is the code that is required to build the same functionality using expression tree.
Expression convertExpr = Expression.Convert(
Expression.Constant(val),
typeof(Int16)
);
Console.WriteLine(Expression.Lambda<Func<Int16>>(convertExpr).Compile()());