C# Is Checkbox Checked In DataGridView

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I am working a utility to build some tables in a proprietary database that we use. I have put a quote in to point out the problem. If that checkbox is checked, then i want to set the value of the pk string to PRIMARY KEY and the fieldname.

I have tried

if (dg[5, i] == checked)

if (dg[5, i])

but so far I have gotten is
Error 1 Operator '==' cannot be applied to operands of type 'object' and 'bool'

public string BuildCreateTableString(System.Windows.Forms.DataGridView dg, string tablename)
        {
            StringBuilder sb = new StringBuilder("");
            string pk = "";
            sb.Append("CREATE TABLE " + tablename + "(");
            int i = 0; // counter for datagrid rows
            while (i < dg.Rows.Count - 1){
                sb.AppendLine("");
                if (i > 0)
                    sb.Append(",");
                sb.Append(dg[0, i].Value);
                sb.AppendFormat("\t\t");
                sb.Append(dg[1, i].Value);
                // culprit
                if (dg[5, i] == true)
                    pk += "Primary Key " + dg[0, i];
                i++;
            }
            sb.Append(pk);
            return sb.ToString();
        }