سلام
زمان اجرای نرم افزار این ارور رو میده .
ضمنا من از vs 2013 استفاده میکنم و توی رفرنس هاSystem.Data.SqlClient.SqlException نیست .
لطفا راهنمایی کنید .
A first chance exception of type 'System.Data.SqlClient.SqlException' occurred in System.Data.dll
Additional information: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified)