You can build an expression tree which contains an assignment operation using Expression.Assign method. For example, you have the following code.
string myString;
myString = "Hello, World!";
Console.WriteLine(myString);
Here is the code that is required to build the same functionality using expression tree.
ParameterExpression myStringVariableExpr = Expression.Variable(typeof(Stri
Expression assignExpr = Expression.Assign(
myStringVariableExpr,
Expression.Constant("Hello, World!")
);
Expression blockExpr = Expression.Block(
new ParameterExpression[] { myStringVariableExpr },
assignExpr
);
Console.WriteLine(Expression.Lambda<Func<String>>(blockExpr).Compile()());