Error: 'BIGINT' trying to update 'STRING' data type

Error: 'BIGINT' trying to update 'STRING' data type

Hello,

I'm trying to fetch data from a report to auto fill a form. When putting in the code, I get an Error. Can someone help me fix this?

Error at line number : 5 
Variable 'First_Name' is already defined of data type 'BIGINT' but trying to update 'STRING' data type

if (OC_Information[ID == input.Employee_ID].count()  >  0)
{
    ocinfo  =  OC_Information  [ID == input.Employee_ID];
    //input. refers to fields in current form 
    input.First_Name = ocinfo.First_Name;