I have the code

if (!(row.IsNull("bigInt") || row["bigInt"].Equals(String.Empty)))
                this.bigInt = Convert.ToInt64(row["bigInt"]);

But, it's give to me the error: Cannot inplicity convert type 'long' to 'int'. An explicit conversion exists (are you missing a cast?)

SQL Server's bigint type maps to Int64 in .NET, so that's right. It looks like you're trying to assign the result of the conversion where it won't fit. What type is this.bigInt?