Lambda Expression比较字符串

Question

我有StartsWith的可行代码，但我需要使用Compare代替StartsWith：

LambdaExpression startsWithLambda = (Expression<Func<string, string, bool>>)((x, s) => x.StartsWith(s)); // works
//  LambdaExpression startsWithLambda = (Expression<Func<string, string, bool>>)((x, s) => string.Compare(x,s) > 0); -  doesn't work

MethodInfo startsWithMI = (startsWithLambda.Body as MethodCallExpression).Method;

ParameterExpression param = Expression.Parameter(typeof(T));
Expression nameProp = Expression.Property(param, _propertyName);

Expression filteredOk = Expression.Constant(true);

Expression startsWithStringExpr = Expression.Constant(_filter);
Expression startsWithCondition = Expression.Call(nameProp, startsWithMI, startsWithStringExpr);

filteredOk = Expression.AndAlso(filteredOk, startsWithCondition);

Expression<Func<T, bool>> where = Expression.Lambda<Func<T, bool>>(filteredOk, new ParameterExpression[] { param });

var result = orderedQuery.Where(where).Take(_linesCount);

如何使用lambda表达式实现string.Compare？

Answer 1

找到解决方案：   表达startsWithCondition = Expression.Call（startsWithMI，nameProp，startsWithStringExpr）;

如果在Call方法中使用静态方法参数应该切换。