The first version was released in year 2002. The latest version, C# 13<\/strong>, was released in November 2024.<\/p>\n\n\n\n \u5982\u4e0a\u6240\u8bf4\uff0cC#\u662f\u9762\u5411\u5bf9\u8c61\u7684\uff0cC# is close to Java\u3001C++ \uff0cC# \u662f 2002 \u5e74\u53d1\u5e03\uff0c\u6700\u65b0\u7684 C# \u7248\u672c\u662f C#13 \u53d1\u5e03\u4e8e 2024 \u5e74\u3002<\/p>\n\n\n\n Variables are containers for storing data values.<\/p>\n\n\n\n In C#, there are different types<\/strong> of variables (defined with different keywords), for example:<\/p>\n\n\n\n \u5728\u4e2d\u6587\u7248\u83dc\u9e1f\u6559\u7a0b\u4e2d\uff0c\u8bf4 C# \u4e2d\u63d0\u4f9b\u7684\u57fa\u672c\u7684\u503c\u7c7b\u578b\u5927\u81f4\u53ef\u4ee5\u5206\u4e3a\u4ee5\u4e0b\u51e0\u7c7b\uff1a<\/em><\/p>\n\n\n\n \u53ef\u4ee5\u53d1\u73b0\uff0c\u548c\u82f1\u6587\u7248 w3schools \u4e2d\u7684\u8bf4\u7684\u7c7b\u578b\u8fd8\u4e0d\u592a\u4e00\u6837\u3002<\/p>\n\n\n\n \u82f1\u6587\u7248 w3schools \u4e2d\u7684\u4f8b\u5b50\uff1a<\/p>\n\n\n\n \u9700\u8981\u6ce8\u610f\u4e00\u70b9\uff1a<\/strong><\/p>\n\n\n\n C# \u4e2d\u7684\u6574\u578b\u5c31\u662f int \u7c7b\u578b\uff0c\u4e0d\u50cf Java \u4e00\u6837\u9664\u4e86 int \u8fd8\u641e\u4e2a Integer \u7c7b\u578b\u3002 If you don’t want others (or yourself) to overwrite existing values, you can add the\u00a0 \u5e38\u91cf\u662f\u56fa\u5b9a\u503c\uff0c\u7a0b\u5e8f\u6267\u884c\u671f\u95f4\u4e0d\u4f1a\u6539\u53d8\u3002\u5e38\u91cf\u53ef\u4ee5\u662f\u4efb\u4f55\u57fa\u672c\u6570\u636e\u7c7b\u578b\uff0c\u6bd4\u5982\u6574\u6570\u5e38\u91cf\u3001\u6d6e\u70b9\u5e38\u91cf\u3001\u5b57\u7b26\u5e38\u91cf\u6216\u8005\u5b57\u7b26\u4e32\u5e38\u91cf\uff0c\u8fd8\u6709\u679a\u4e3e\u5e38\u91cf\u3002 \u5e38\u91cf\u662f\u4f7f\u7528\u00a0const<\/strong>\u00a0\u5173\u952e\u5b57\u6765\u5b9a\u4e49\u7684 \u3002 This will declare the variable as “constant”, which means unchangeable and read-only:<\/p>\n\n\n\n <\/p>\nThe\u00a0 As explained in the variables chapter, a variable in C# must be a specified data type:<\/p>\n\n\n\n A data type specifies the size and type<\/strong><\/em> of variable values.It is important to use the correct data type for the corresponding variable; to avoid errors, to save time and memory, but it will also make your code more maintainable and readable. The most common data types are:<\/p><\/p>\n\n\n\n C# \u83dc\u9e1f\u6559\u7a0b\u4e2d\u662f\u8fd9\u6837\uff1a<\/p>\n\n\n\n \u76f8\u6bd4\u4e4b\u4e0b\uff1a<\/p>\n\n\n\n \u66f4\u591a\u7c7b\u578b\u4ecb\u7ecd\uff1ahttps:\/\/www.w3schools.com\/cs\/cs_data_types.php<\/a><\/p>\n\n\n\n Type casting is when you assign a value of one data type to another type.<\/p>\n\n\n\n In C#, there are two types of casting:<\/p>\n\n\n\n Implicit casting is done automatically when passing a smaller size type to a larger size type:<\/p>\n\n\n\n Explicit casting must be done manually by placing the type in parentheses in front of the value:<\/p>\n\n\n\n \u4e0a\u9762\u90fd\u662f\u201c\u6570\u5b57\u201d\u4e4b\u95f4\u7684\u8f6c\u6362\uff0c\u5982\u679c\u662f\u201c\u6570\u5b57\u201d\u548c\u201c\u5b57\u7b26\u4e32\u201d\u4e4b\u95f4\u7684\u8f6c\u6362\u5462\uff1f<\/strong><\/mark><\/p>\n\n\n\n <\/mark><\/mark><\/strong><\/p>\n\n\n\n It is also possible to convert data types explicitly by using built-in methods, such as\u00a0 C# \u4e2d\u5185\u7f6e\u4e86\u5f88\u591a\u4e0d\u540c\u7c7b\u578b\u4e4b\u95f4\u7684\u8f6c\u6362\u65b9\u6cd5\uff0c\u8fd9\u4e9b\u65b9\u6cd5\u90fd\u5b9a\u4e49\u5728 System.Convert \u7c7b\u4e2d\uff0c\u4f7f\u7528\u65f6\u9700\u8981\u5305\u542b System \u547d\u540d\u7a7a\u95f4\u3002\u5b83\u4eec\u63d0\u4f9b\u4e86\u4e00\u79cd\u5b89\u5168\u7684\u65b9\u5f0f\u6765\u6267\u884c\u7c7b\u578b\u8f6c\u6362\uff0c\u56e0\u4e3a\u5b83\u4eec\u53ef\u4ee5\u5904\u7406 null\u503c\uff0c\u5e76\u4e14\u4f1a\u629b\u51fa\u5f02\u5e38\uff0c\u5982\u679c\u8f6c\u6362\u4e0d\u53ef\u80fd\u8fdb\u884c\u3002<\/p>\n\n\n\n \u66f4\u591a\u7c7b\u578b\u8f6c\u6362\u89c1\uff1ahttps:\/\/www.runoob.com\/csharp\/csharp-type-conversion.html<\/a><\/p>\n\n\n\n Arithmetic operators<\/strong> are used to perform common mathematical operations<\/strong>: \u3010\u8fd0\u7b97\u7b26\u548c Java \u57fa\u672c\u4e00\u6837\u3011<\/p>\n\n\n\n As with comparison operators<\/a>, you can also test for Logical operators are used to determine the logic between variables or values:<\/p>\n\n\n\n There are many array methods available, for example Other useful array methods, such as In the previous chapter, you learned about\u00a0<\/span>arrays<\/a>, which is also known as\u00a0<\/span>single dimension arrays<\/strong>. These are great, and something you will use a lot while programming in C#. However, if you want to store data as a tabular form, like a table with rows and columns, you need to get familiar with\u00a0<\/span>multidimensional arrays<\/strong>.A multidimensional array is basically an array of arrays.Arrays can have any number of dimensions. The most common are two-dimensional arrays (2D).<\/p><\/p>\n\n\n\n To create a 2D array, add each array within its own set of curly braces, and insert a comma ( Good to know:<\/strong>\u00a0<\/span>The single comma\u00a0<\/span><\/span> To access an element of a two-dimensional array, you must specify two indexes: one for the array, and one for the element inside that array. Or better yet, with the table visualization in mind; one for the row and one for the column (see example below).<\/p>\n\n\n\nWhy Use C#?<\/h1>\n\n\n\n
\n
C# Output<\/h1>\n\n\n\n
Console.WriteLine(\"Hello World!\");\/\/\u4f1a\u6362\u884c Note that it will add a new line for each method\nConsole.Write(\"Hello World! \");\/\/\u4e0d\u6362\u884c it does not insert a new line at the end of the output<\/code><\/pre>\n\n\n\nC# Variables<\/h1>\n\n\n\n
\n
int<\/strong><\/code>\u00a0– stores integers (whole numbers), without decimals<\/strong><\/mark>, such as 123 or -123<\/li>\n\n\n\ndouble<\/code>\u00a0<\/strong>– stores floating point numbers, with decimals<\/mark><\/strong>, such as 19.99 or -19.99<\/li>\n\n\n\nchar<\/code>\u00a0<\/strong>– stores single characters, such as ‘a’ or ‘B’. Char values are surrounded by single quotes<\/li>\n\n\n\nstring<\/code>\u00a0<\/strong>– stores text, such as “Hello World”. String values are surrounded by double quotes<\/li>\n\n\n\nbool<\/code>\u00a0<\/strong>– stores values with two states: true or false<\/li>\n<\/ul>\n\n\n\n![\"\"](\"http:\/\/codermr.com\/wp-content\/uploads\/2025\/03\/image-1.png\")
<\/a><\/figure>\n\n\n\nint myNum = 5;\ndouble myDoubleNum = 5.99D;\nchar myLetter = 'D';\nbool myBool = true;\nstring myText = \"Hello\";<\/code><\/pre>\n\n\n\n
C# \u4e2d\u7684\u7c7b\u578b\u540d\uff0c\u90fd\u662f\u5c0f\u5199\u7684\uff0c\u5982 int\u3001string\u3001char \u7b49\uff0c\u4e0d\u50cf Java \u4e00\u6837\u662f String \u3001Boolean \u7b49\u7b49\u3002<\/p>\n\n\n\nC#\u00a0Constants \u5e38\u91cf<\/h1>\n\n\n\n
Constants<\/h2>\n\n\n\n
const<\/code>\u00a0keyword in front of the variable type.<\/p>\n\n\n\n
\u5e38\u91cf\u53ef\u4ee5\u88ab\u5f53\u4f5c\u5e38\u89c4\u7684\u53d8\u91cf\uff0c\u53ea\u662f\u5b83\u4eec\u7684\u503c\u5728\u5b9a\u4e49\u540e\u4e0d\u80fd\u88ab\u4fee\u6539\u3002<\/p>\n\n\n\n
\u4f7f\u7528 const<\/strong>\u00a0\u7684\u65b9\u6cd5\uff0c\u5c31\u662f\u5c06 const<\/strong>\u00a0\u5173\u952e\u5b57\u5199\u5728\u7c7b\u578b\u7684\u524d\u9762\u3002<\/mark><\/p>\n\n\n\nconst int myNum = 15;\nmyNum = 20; \/\/ error<\/code><\/pre>\n\n\n\n\n
const<\/code>\u00a0keyword is useful when you want a variable to always store the same value, so that others (or yourself) won’t mess up<\/mark><\/strong> your code. An example that is often referred to as a constant, is PI (3.14159…).
Note:<\/strong>\u00a0You cannot declare a constant variable without assigning the value<\/mark><\/strong>. If you do, an error will occur:\u00a0A const field requires a value to be provided.<\/cite><\/blockquote>\n\n\n\nC# Data Types<\/h1>\n\n\n\n
int myNum = 5; \/\/ Integer (whole number)\ndouble myDoubleNum = 5.99D; \/\/ Floating point number\nchar myLetter = 'D'; \/\/ Character\nbool myBool = true; \/\/ Boolean\nstring myText = \"Hello\"; \/\/ String<\/code><\/pre>\n\n\n\n![\"\"](\"http:\/\/codermr.com\/wp-content\/uploads\/2025\/03\/image-8.png\")
<\/a><\/figure>\n\n\n\n![\"\"](\"http:\/\/codermr.com\/wp-content\/uploads\/2025\/03\/image-3.png\")
<\/a><\/figure>\n\n\n\n![\"\"](\"http:\/\/codermr.com\/wp-content\/uploads\/2025\/03\/image-4.png\")
<\/a><\/figure>\n\n\n\nC# Type Casting<\/h1>\n\n\n\n
\n
char<\/code>\u00a0->\u00a0int<\/code>\u00a0->\u00a0long<\/code>\u00a0->\u00a0float<\/code>\u00a0->\u00a0double<\/code>
<\/li>\n\n\n\ndouble<\/code>\u00a0->\u00a0float<\/code>\u00a0->\u00a0long<\/code>\u00a0->\u00a0int<\/code>\u00a0->\u00a0char<\/code><\/li>\n<\/ul>\n\n\n\nImplicit Casting<\/h2>\n\n\n\n
int myInt = 9;\ndouble myDouble = myInt; \/\/ Automatic casting: int to double \u3010\u4ece\u201csmall size\u201d\u5f80\u201clarger size\u201d\u8f6c\u6362\u4e0d\u8981\u5f3a\u8f6c\u3001\u4e0d\u7528\u52a0\u62ec\u53f7\u3011<\/strong><\/mark>\n\nConsole.WriteLine(myInt); \/\/ Outputs 9\nConsole.WriteLine(myDouble); \/\/ Outputs 9<\/code><\/pre>\n\n\n\nExplicit Casting<\/h2>\n\n\n\n
double myDouble = 9.78;\nint myInt = (int) myDouble; \/\/ Manual casting: double to int\u3010\u4ece\u201clarger<\/strong><\/mark> size\u201d\u5f80\u201csmall<\/strong><\/mark> size\u201d\u8f6c\u6362\u9700\u8981\u5f3a\u8f6c\u3001\u9700\u8981\u52a0\u62ec\u53f7\uff0c\u4e14\u53ef\u80fd\u4e22\u5931\u7cbe\u5ea6\u3011<\/strong><\/mark>\n\nConsole.WriteLine(myDouble); \/\/ Outputs 9.78\nConsole.WriteLine(myInt); \/\/ Outputs 9<\/code><\/pre>\n\n\n\nint a = 1;\nstring b = 1 + \"\"; \/\/ \u50cf Java \u4e00\u6837\uff0c\u5c06\u6570\u5b57\u548c\u5b57\u7b26\u4e32\u7528 + \u53f7\u8fde\u63a5\u5373\u53ef\u3002<\/code><\/pre>\n\n\n\nType Conversion Methods . C# \u63d0\u4f9b\u7684\u4e0d\u540c\u7c7b\u578b\u4e4b\u95f4\u8f6c\u6362\u7684\u65b9\u6cd5<\/h2>\n\n\n\n
Convert.ToBoolean<\/code>,\u00a0Convert.ToDouble<\/code>,\u00a0Convert.ToString<\/code>,\u00a0Convert.ToInt32<\/code>\u00a0(int<\/code>) and\u00a0Convert.ToInt64<\/code>\u00a0(long<\/code>): \u3010\u6709\u70b9\u7c7b\u4f3c\u4e8e Java \u4e2d\u7684 String.valueOf(..)\u3001Integer.parseInt(…)<\/mark><\/strong>\u3011<\/mark><\/mark><\/strong><\/p>\n\n\n\nint myInt = 10;\ndouble myDouble = 5.25;\nbool myBool = true;\n\nConsole.WriteLine(Convert.ToString(myInt)); \/\/ convert int to string<\/mark><\/strong>\nConsole.WriteLine(Convert.ToDouble(myInt)); \/\/ convert int to double<\/mark><\/strong>\nConsole.WriteLine(Convert.ToInt32(myDouble)); \/\/ convert double to int<\/mark><\/strong>\nConsole.WriteLine(Convert.ToString(myBool)); \/\/ convert bool to string<\/mark><\/strong><\/code><\/pre>\n\n\n\n![\"\"](\"http:\/\/codermr.com\/wp-content\/uploads\/2025\/03\/image-5.png\")
<\/a><\/figure>\n\n\n\nArithmetic Operators<\/h1>\n\n\n\n
![\"\"](\"http:\/\/codermr.com\/wp-content\/uploads\/2025\/03\/image-7.png\")
<\/a><\/figure>\n\n\n\nLogical Operators<\/h1>\n\n\n\n
True<\/code> or False<\/code> values with logical operators<\/strong>.<\/p>\n\n\n\n<\/p>\n\n\n\n
C#\u00a0For Loop<\/h1>\n\n\n\n
for (int i = 0; i < 5; i++) \n{\n Console.WriteLine(i);\n}<\/code><\/pre>\n\n\n\nC#\u00a0Foreach Loop<\/h2>\n\n\n\n
string[] cars = {\"Volvo\", \"BMW\", \"Ford\", \"Mazda\"};\nforeach (string i in cars) \n{\n Console.WriteLine(i);\n}<\/code><\/pre>\n\n\n\nC#\u00a0Arrays \u3010\u548c Java \u4e2d\u7684\u5dee\u4e0d\u591a\u3011<\/h1>\n\n\n\n
string[] cars = {\"Volvo\", \"BMW\", \"Ford\", \"Mazda\"};<\/code><\/pre>\n\n\n\nSort an Array \u3010\u6570\u7ec4\u6392\u5e8f\uff01\uff01\uff01\u3011<\/h2>\n\n\n\n
Sort()<\/code>, which sorts an array alphabetically or in an ascending order:<\/p>\n\n\n\n\/\/ Sort a string\nstring[] cars = {\"Volvo\", \"BMW\", \"Ford\", \"Mazda\"};\nArray.Sort(cars); \/\/ \u2588\u2588 Array.Sort(...) \nforeach (string i in cars)\n{\n Console.WriteLine(i);\n}\n\n\/\/ Sort an int\nint[] myNumbers = {5, 1, 8, 9};\nArray.Sort(myNumbers);\nforeach (int i in myNumbers)\n{\n Console.WriteLine(i);\n}<\/code><\/pre>\n\n\n\nSystem.Linq Namespace \u2588\u2588 \u4f7f\u7528 Linq \u6392\u5e8f\uff01\uff01\uff01<\/h2>\n\n\n\n
Min<\/code>, Max<\/code>, and Sum<\/code>, can be found in the System.Linq<\/code> namespace:<\/p>\n\n\n\nusing System;\nusing System.Linq;\n\nnamespace MyApplication\n{\n class Program\n {\n static void Main(string[] args)\n {\n int[] myNumbers = {5, 1, 8, 9};\n Console.WriteLine(myNumbers.Max()); \/\/ returns the largest value\n Console.WriteLine(myNumbers.Min()); \/\/ returns the smallest value\n Console.WriteLine(myNumbers.Sum()); \/\/ returns the sum of elements\n }\n }\n}<\/code><\/pre>\n\n\n\nC#\u00a0Multidimensional Arrays \u591a\u7ef4\u6570\u7ec4<\/h2>\n\n\n\n
Two-Dimensional Arrays<\/h2>\n\n\n\n
,<\/code>) inside the square brackets:<\/p>\n\n\n\nint[,] numbers = { {1, 4, 2}, {3, 6, 8} };<\/code><\/pre>\n\n\n\n[,]<\/code>\u00a0<\/span>specifies that the array is two-dimensional. A three-dimensional array would have two commas:\u00a0<\/span><\/span>int[,,]<\/code>.<\/span><\/p>\n\n\n\nnumbers<\/code>\u00a0is now an array with two arrays as its elements. The first array element contains three elements: 1, 4 and 2, while the second array element contains 3, 6 and 8. To visualize it, think of the array as a table with rows and columns:<\/p>\n\n\n\n![\"\"](\"http:\/\/codermr.com\/wp-content\/uploads\/2025\/03\/image-9.png\")
<\/a><\/figure>\n\n\n\nAccess Elements of a 2D Array<\/h2>\n\n\n\n