2015-10-04-create-lambda-expressions-on-the-fly-in-c_008.cs

public Expression<Func<T, bool>> GetExpressionForType<TEntity>(string field, string operation, object value, string ignoreCase) 
{ 
  Expression<Func<T, bool>> whereClause = default(Expression<Func<T, bool>>); 
  ParameterExpression param = Expression.Parameter(typeof(T), "x"); 
  MemberExpression member = Expression.Property(param, field); 
  Type propertyType = member.Type; 
  TypeConverter converter = TypeDescriptor.GetConverter(propertyType); 
    
  var result = converter.ConvertFrom(value.ToString()); 
  ConstantExpression constant = Expression.Constant(result); 
  Expression comparingExpression = default(BinaryExpression); 
    
  switch (operation) 
  {
    case "eq": 
      comparingExpression = Expression.Equal(member, Expression.Convert(constant, member.Type));
      break;         
    case "startswith": 
      MethodInfo startsWithMethodInfo = typeof(string).GetMethod("StartsWith", new Type[] { typeof(string) }); 
      comparingExpression = Expression.Call(member, startsWithMethodInfo, Expression.Convert(constant, member.Type)); 
      break; 
  }     
  ...
}