Local variable and expression trees

Question

I am learning expression trees in C#.

I am stuck now for a while:

string filterString = \"ruby\";
Expression> expressi         


        

Answer 1

This code wraps the expression in a closure Block that treats the local variable as a constant.

 string filterString = "ruby";

 var filterStringParam = Expression.Parameter(typeof(string), "filterString");
 var stringParam = Expression.Parameter(typeof(string), "x");

 var block = Expression.Block(
 // Add a local variable.
 new[] { filterStringParam },
 // Assign a constant to the local variable: filterStringParam = filterString
 Expression.Assign(filterStringParam, Expression.Constant(filterString, typeof(string))),
 // Compare the parameter to the local variable
 Expression.Equal(stringParam, filterStringParam));

 var x = Expression.Lambda>(block, stringParam).Compile();