How can I use warm start in C#

I have been working on an MIP in C#. I want to reduce the gap, so I’m trying warm start. I use this code just before solve().

try
    {
        startvar = new IIntVar[numberOfAllNode * numberOfAllNode];
        startval = new double[numberOfAllNode * numberOfAllNode];

        for (int j = 1, idx = 0; j <= numberOfAllNode; j++)
            for (int i = 1; i <= numberOfAllNode; i++)
            {
                startvar[idx] = x[j][i];
                startval[idx] = x_value[j,i];
                idx++;
            }

        startvar = null;
        startval = null;
        Cplex.AddMIPStart(startvar[], startval[], Cplex.MIPStartEffort.SolveMIP);
    }

I got some syntax errors in the last line. unfortunately, I don’t know what variable should I write in startvar[].