Data types in C # for field types in the database (reproduced)

The field type in the database corresponds to the data type in C #: Database C # program
int int32
Text string
bigint Int64
Binary system.byte[]
Bit Boolean
Char string
DateTime System.DateTime
Decimal System.Decimal
Float System.Double
Image system.byte[]
Money System.Decimal
NCHAR String
ntext String
Numeric System.Decimal
nvarchar String
Real System.Single
smalldatetime System.DateTime
smallint Int16
SmallMoney System.Decimal
Timestamp System.DateTime
tinyint System.Byte
uniqueidentifier System.Guid
varbinary system.byte[]
varchar String
Variant Object a detailed description of the relevant field types in the database:

Data type	Type	Description
Bit	Integral type	The bit data type is integral, and its value can only be 0, 1, or null. This data type is used to store data with only two possible values, such as Yes or No, True or false, on, or off
Int	Integral type	The int data type can store integers from 231 (-2147483648) to 231 (2147483 647). Almost all numeric data stored in a database can be used with this data type. This type of data occupies 4 bytes in the database.
smallint	Integral type	The smallint data type can store integers from 215 (-32768) to 215 (32767). This data type is useful for storing numeric data that is often scoped to a specific range. This data type occupies 2 bytes of space in the database.
tinyint	Integral type	The tinyint data type can store integers from 0 to 255. It is useful when you only intend to store a limited number of values. This data type occupies 1 bytes in a database
Numeric	Precise numerical type	The numeric data type is the same as the decimal type
Decimal	Precise numerical type	The decimal data type can be used to store numeric data of fixed precision and range from 1038-1 to 1038-1. When you use this data type, you must specify the range and precision. The range is the total number of digits that can be stored around the decimal point. Precision is the number of digits stored on the right of the decimal point
Money	Currency type	The Money data type is used to denote monetary and currency values. This data type can store data from 922 billion to 922 billion, accurate to one out of 10,000 of the currency unit
SmallMoney	Currency type	The smallmoney data type is used to represent money and currency values. This data type can store data from 214748.3648 to 214748.3647, accurate to one out of 10,000 of the currency unit
Float	Approximate numerical type	The float data type is an approximate numeric type that is used by floating point numbers. It is said that the floating-point number is approximate, because not all the numbers in its range can be accurately represented. Floating-point numbers can be any number from -1.79E+308 to 1.79E+308
Real	Approximate numerical type	Real data types are approximate numeric types like floating-point numbers. It can represent a floating-point number between -3.40E+38 and 3.40E+38.
Datetime	Date-Time Type	The datetime data type is used to represent the date and time. This data type stores all date and time data from January 1, 1753 to December 9999 3 1st, accurate to 1% seconds or 3.33 milliseconds
smalldatetime	Date-Time Type	The smalldatetime data type is used to represent the date and time from January 1, 1900 to June 6, 2079, accurate to one minute
Cursor	Special Data type	The cursor data type is a special type of data that contains a reference to a cursor. This data type is used in stored procedures and cannot be used when creating tables
Timestamp	Special Data type	The timestamp data type is a special type of data that is used to create a database-wide unique digital. There can be only one timestamp column in a table. Each time you insert or modify a row, the value of the timestamp column changes. Although it has "time" in its name, the timestamp column is not a date that people can recognize. In a database, the timestamp value is unique.
uniqueidentifier	Special Data type	The uniqueidentifier data type is used to store a globally unique identifier, the GUID. The GUID is truly globally unique. This number has little chance of being rebuilt in another system. You can initialize a column with a unique identifier by using the NEWID function or by converting a string to a unique identifier
Char	Character type	The char data type is used to store fixed-length, non-uniform encoded data of specified lengths. When you define a column for this type, you must specify a column length. This data type is useful when you always know the length of the data you want to store. For example, when you store data by zip code plus 4 character formatting, you know that you always need to use 10 characters. This data type has a maximum width of 8,000 characters
varchar	Character type	The varchar data type, like the char type, is used to store non-uniform encoded character data. Unlike the char type, this data type is variable length. When you define a column for that data type, you specify the maximum length of the columns. The biggest difference to the char data type is that the length of the store is not a column long, but the length of the data
Text	Character type	The text data type is used to store a large number of non-uniform encoded character data. This data type can have a maximum of 231-1 or 2 billion characters
NChar	Unified coded Character type	The nchar data type is used to store fixed-length, uniformly encoded character data. Uniform encoding uses a double-byte structure to store each character, rather than a single byte (in normal text). It allows for a large number of extended characters. This data type can store 4000 characters, increasing the byte space used by
nvarchar	Unified coded Character type	The nvarchar data type is used as a uniformly encoded character type data that is variable length. This data type can store 4000 characters, using a byte space increase of one
ntext	Unified coded Character type	The ntext data type is used to store a large number of uniformly encoded character-type data. This data type can store 230-1 or nearly 1 billion characters, and the byte space used increases by one times
Binary	Binary data types	Binary data types are used to store fixed-length binary data up to 8000 bytes long. You should use this data type when the contents of the input table are close to the same length
varbinary	Binary data types	The varbinary data type is used to store variable-length binary data up to 8000 bytes long. You should use this data type when the content size of the input table is variable
Image	Binary data types	The image data type is used to store variable-length binary data up to 231-1 or approximately 2 billion bytes

Data types in C # for field types in the database (reproduced)