How to save values in EchMultiselect with name instead of dropDownAttribute

I am always getting only one values even though i have selected multiple of data.If i use dropDownAttribute instead of name ,then it works but if I want to update it doesn’t work with dropDownAttribute but shows the value while using name. So i want to use name instead of dropDownAttribute in EchMultiselect,but the problem is it doesn’t save the multiple selected value