我遇到了一个巨大的方法，其中有很多类型的if else语句
else if (ptName == "Missile" ||
ptName == "Telephone" ||
(ptName.StartsWith("Car") && gasTank.ValueFloat1.Value < 90))
{
foo_1 = "some_string";
}
不幸的是，此代码并不完全正确，因为变量gasTank仅在ptName以字符串“ Car”开头的情况下定义。因此，在运行时我得到了
发生InvalidOperationException：空对象必须具有一个值。
这可以通过嵌套ifs和else ifs以及重复条件ptName.StartsWith("Car")来解决，尽管这是非常不希望的。
将方法拆分为许多小方法或在每个条件之后添加return都不是一种选择，因为该方法的return是各种foo_i的串联。
先谢谢您。
答案 0 :(得分：4)
条件
0000A2 slice_layer_without_partitioning (IDR) - 0 (0x0) - Frame 0 - slice_type I - frame_num 0 - DTS 00:00:00.000 - PTS 00:00:00.017 (141867 bytes)
0000A2 Header (5 bytes)
0000A2 zero_byte: 0 (0x00)
0000A3 start_code_prefix_one_3bytes: 1 (0x000001)
0000A6 nal_ref_idc: 3 (0x3) - (2 bits)
0000A6 nal_unit_type: 5 (0x05) - (5 bits)
0000A7 slice_header (3 bytes)
0000A7 first_mb_in_slice: 0 (0x0)
0000A7 slice_type: 7 (0x07) - I
0000A8 pic_parameter_set_id: 0 (0x0)
0000A8 frame_num: 0 (0x0)
0000A8 idr_pic_id: 0 (0x0)
0000A8 no_output_of_prior_pics_flag: No
0000A8 long_term_reference_flag: No
0000A9 slice_qp_delta: -5 (0xFFFFFFFB)
0000AA disable_deblocking_filter_idc: 0 (0x0)
0000AA slice_alpha_c0_offset_div2: 0 (0x0)
0000AA slice_beta_offset_div2: 0 (0x0)
0000AA slice_data (141856 bytes)
0000AA (ToDo): (Data)
022ACD slice_layer_without_partitioning (IDR) - 0 (0x0) - Frame 0 - slice_type I - frame_num 0 - DTS 00:00:00.000 - PTS 00:00:00.017 - first_mb_in_slice 8040 (2248 bytes)
022ACD Header (5 bytes)
022ACD zero_byte: 0 (0x00)
022ACE start_code_prefix_one_3bytes: 1 (0x000001)
022AD1 nal_ref_idc: 3 (0x3) - (2 bits)
022AD1 nal_unit_type: 5 (0x05) - (5 bits)
022AD2 slice_header (6 bytes)
022AD2 first_mb_in_slice: 8040 (0x001F68)
022AD5 slice_type: 7 (0x07) - I
022AD6 pic_parameter_set_id: 0 (0x0)
022AD6 frame_num: 0 (0x0)
022AD6 idr_pic_id: 0 (0x0)
022AD6 no_output_of_prior_pics_flag: No
022AD6 long_term_reference_flag: No
022AD7 slice_qp_delta: -5 (0xFFFFFFFB)
022AD8 disable_deblocking_filter_idc: 0 (0x0)
022AD8 slice_alpha_c0_offset_div2: 0 (0x0)
022AD8 slice_beta_offset_div2: 0 (0x0)
022AD8 slice_data (2237 bytes)
022AD8 (ToDo): (Data)
023395 1 (36212 bytes)
023395 slice_layer_without_partitioning (non-IDR) - 2 (0x2) - Frame 1 - slice_type P - frame_num 1 - DTS 00:00:00.000 (36017 bytes)
023395 Header (5 bytes)
023395 zero_byte: 0 (0x00)
023396 start_code_prefix_one_3bytes: 1 (0x000001)
023399 nal_ref_idc: 3 (0x3) - (2 bits)
023399 nal_unit_type: 1 (0x01) - (5 bits)
02339A slice_header (3 bytes)
02339A first_mb_in_slice: 0 (0x0)
02339A slice_type: 5 (0x5) - P
02339A pic_parameter_set_id: 0 (0x0)
02339A frame_num: 1 (0x1)
02339B num_ref_idx_active_override_flag (0 bytes)
02339B num_ref_idx_active_override_flag: Yes
02339B num_ref_idx_l0_active_minus1: 0 (0x0)
02339B ref_pic_list_modification_flag_l0: No
02339B adaptive_ref_pic_marking_mode_flag: No
02339C cabac_init_idc: 0 (0x0)
02339C slice_qp_delta: -3 (0xFFFFFFFD)
02339C disable_deblocking_filter_idc: 0 (0x0)
02339C slice_alpha_c0_offset_div2: 0 (0x0)
02339D slice_beta_offset_div2: 0 (0x0)
02339D slice_data (36012 bytes)
02339D (ToDo): (Data)
02C046 slice_layer_without_partitioning (non-IDR) - 2 (0x2) - Frame 1 - slice_type P - frame_num 1 - DTS 00:00:00.000 - first_mb_in_slice 8040 (195 bytes)
02C046 Header (5 bytes)
02C046 zero_byte: 0 (0x00)
02C047 start_code_prefix_one_3bytes: 1 (0x000001)
02C04A nal_ref_idc: 3 (0x3) - (2 bits)
02C04A nal_unit_type: 1 (0x01) - (5 bits)
02C04B slice_header (6 bytes)
02C04B first_mb_in_slice: 8040 (0x001F68)
02C04E slice_type: 5 (0x5) - P
02C04E pic_parameter_set_id: 0 (0x0)
02C04E frame_num: 1 (0x1)
02C04F num_ref_idx_active_override_flag (0 bytes)
02C04F num_ref_idx_active_override_flag: Yes
02C04F num_ref_idx_l0_active_minus1: 0 (0x0)
02C04F ref_pic_list_modification_flag_l0: No
02C04F adaptive_ref_pic_marking_mode_flag: No
02C050 cabac_init_idc: 0 (0x0)
02C050 slice_qp_delta: -3 (0xFFFFFFFD)
02C050 disable_deblocking_filter_idc: 0 (0x0)
02C050 slice_alpha_c0_offset_div2: 0 (0x0)
02C051 slice_beta_offset_div2: 0 (0x0)
02C051 slice_data (190 bytes)
02C051 (ToDo): (Data)
02C109 1 (26280 bytes)
02C109 slice_layer_without_partitioning (non-IDR) - 4 (0x4) - Frame 2 - slice_type P - frame_num 2 - DTS 00:00:00.000 (26157 bytes)
02C109 Header (5 bytes)
02C109 zero_byte: 0 (0x00)
02C10A start_code_prefix_one_3bytes: 1 (0x000001)
02C10D nal_ref_idc: 3 (0x3) - (2 bits)
02C10D nal_unit_type: 1 (0x01) - (5 bits)
02C10E slice_header (3 bytes)
02C10E first_mb_in_slice: 0 (0x0)
02C10E slice_type: 5 (0x5) - P
02C10E pic_parameter_set_id: 0 (0x0)
02C10E frame_num: 2 (0x2)
02C10F num_ref_idx_active_override_flag (0 bytes)
02C10F num_ref_idx_active_override_flag: Yes
02C10F num_ref_idx_l0_active_minus1: 0 (0x0)
02C10F ref_pic_list_modification_flag_l0: No
02C10F adaptive_ref_pic_marking_mode_flag: No
02C110 cabac_init_idc: 0 (0x0)
02C110 slice_qp_delta: -2 (0xFFFFFFFE)
02C110 disable_deblocking_filter_idc: 0 (0x0)
02C110 slice_alpha_c0_offset_div2: 0 (0x0)
02C111 slice_beta_offset_div2: 0 (0x0)
02C111 slice_data (26152 bytes)
02C111 (ToDo): (Data)
032736 slice_layer_without_partitioning (non-IDR) - 4 (0x4) - Frame 2 - slice_type P - frame_num 2 - DTS 00:00:00.000 - first_mb_in_slice 8040 (123 bytes)
032736 Header (5 bytes)
032736 zero_byte: 0 (0x00)
032737 start_code_prefix_one_3bytes: 1 (0x000001)
03273A nal_ref_idc: 3 (0x3) - (2 bits)
03273A nal_unit_type: 1 (0x01) - (5 bits)
03273B slice_header (6 bytes)
03273B first_mb_in_slice: 8040 (0x001F68)
03273E slice_type: 5 (0x5) - P
03273E pic_parameter_set_id: 0 (0x0)
03273E frame_num: 2 (0x2)
03273F num_ref_idx_active_override_flag (0 bytes)
03273F num_ref_idx_active_override_flag: Yes
03273F num_ref_idx_l0_active_minus1: 0 (0x0)
03273F ref_pic_list_modification_flag_l0: No
03273F adaptive_ref_pic_marking_mode_flag: No
032740 cabac_init_idc: 0 (0x0)
032740 slice_qp_delta: -2 (0xFFFFFFFE)
032740 disable_deblocking_filter_idc: 0 (0x0)
032740 slice_alpha_c0_offset_div2: 0 (0x0)
032741 slice_beta_offset_div2: 0 (0x0)
032741 slice_data (118 bytes)
032741 (ToDo): (Data)
0327B1 1 (21125 bytes)
应该成为
ptName.StartsWith("Car")
那将使您摆脱ptName?.StartsWith("Car") ?? false
的价值。
如果您使用的是低于6的C＃版本，则应使用：
null另一个更新：
ptNAme == null ? false : ptName.StartsWith("Car")
或
(gasTank.ValueFloat1?.Value ?? 0) < 90