update example cover basic crud (#25)

Author: WeihanLi

example/GetStarted/Program.cs

@@ -5,7 +5,8 @@
 
 var connString = Environment.GetEnvironmentVariable("GaussdbConnString");
 ArgumentNullException.ThrowIfNull(connString);
-
+// ReSharper disable AccessToDisposedClosure
+// Dispose will be handled
 await using var conn = new GaussDBConnection(connString);
 if (conn.State is ConnectionState.Closed)
 {
@@ -14,34 +15,139 @@
 
 Console.WriteLine($@"Connection state: {conn.State}");
 
+await ConnectionTest();
+
+var tableName = "employees";
+// id int, name varchar(128), age int
 {
-    await TestScalar();
-    await TestReader();
+    await ExecuteTableScript(async () =>
+    {
+        // insert
+        {
+            var insertSql = $"""
+                             INSERT INTO {tableName} (id, name, age) VALUES
+                             (1, 'John', 30),
+                             (2, 'Alice', 16),
+                             (3, 'Mike', 24)
+                             """;
+            await using var cmd = new GaussDBCommand(insertSql, conn);
+            await cmd.ExecuteNonQueryAsync();
+            Console.WriteLine(@"insert script executed");
+        }
+
+        // query
+        {
+            await QueryTest();
+        }
+
+        // update
+        {
+            var updateSql = $"""
+                             UPDATE {tableName}
+                             SET age = 18
+                             WHERE name = @name
+                             """;
+            await using var cmd = new GaussDBCommand(updateSql, conn);
+            cmd.Parameters.AddWithValue("name", "Alice");
+            await cmd.ExecuteNonQueryAsync();
+            Console.WriteLine(@"update script executed");
+        }
+
+        // query
+        {
+            await QueryTest("age >= 18");
+        }
+
+        // delete
+        {
+            var deleteSql = $"""
+                             DELETE FROM {tableName}
+                             WHERE age > @age
+                             """;
+            await using var cmd = new GaussDBCommand(deleteSql, conn);
+            cmd.Parameters.AddWithValue("age", 10);
+            await cmd.ExecuteNonQueryAsync();
+            Console.WriteLine(@"delete script executed");
+        }
+
+        // query count
+        {
+            var queryCountSql = $"SELECT COUNT(*) FROM {tableName}";
+            await using var cmd = new GaussDBCommand(queryCountSql, conn);
+            var result = await cmd.ExecuteScalarAsync();
+            var count = Convert.ToInt32(result);
+            Console.WriteLine($@"count: {count}");
+        }
+    });
 }
 
 Console.WriteLine(@"Completed!");
 
 
-async Task TestScalar()
+async Task ConnectionTest()
 {
     await using var cmd = new GaussDBCommand("SELECT 1", conn);
     var result = await cmd.ExecuteScalarAsync();
     Console.WriteLine(result);
 }
 
-async Task TestReader()
+async Task ExecuteTableScript(Func<Task> func)
 {
-    await using (var cmd = new GaussDBCommand("SELECT * FROM employees", conn))
+    var createTableSql = $"""
+               DROP TABLE IF EXISTS {tableName} CASCADE;
+               CREATE TABLE {tableName}
+               (
+                   id INT PRIMARY KEY,
+                   name VARCHAR(128),
+                   age INT
+               );
+               """;
+    var dropTableSql = $"DROP TABLE IF EXISTS {tableName} CASCADE;";
+
+    try
+    {
+        await using var createTableCommand = new GaussDBCommand(createTableSql, conn);
+        await createTableCommand.ExecuteNonQueryAsync();
+
+        await func();
+    }
+    catch (Exception ex)
+    {
+        Console.WriteLine(ex);
+    }
+    finally
+    {
+        try
+        {
+            await using var dropTableCommand = new GaussDBCommand(dropTableSql, conn);
+            await dropTableCommand.ExecuteNonQueryAsync();
+        }
+        catch (Exception e)
+        {
+            Console.WriteLine($@"Exception when drop table {tableName} {e}");
+        }
+    }
+
+}
+
+async Task QueryTest(string? condition = null)
+{
+    var sql = $"SELECT * FROM {tableName}";
+    if (!string.IsNullOrEmpty(condition))
+    {
+        sql += $" WHERE {condition}";
+    }
+    Console.WriteLine($@"Executing query {sql}");
+    await using (var cmd = new GaussDBCommand(sql, conn))
     {
         await using var reader = await cmd.ExecuteReaderAsync();
         while (await reader.ReadAsync())
         {
-            // 读取每一行数据
-            var id = reader.GetInt32(0); // 假设第一列是ID，类型为int
-            var name = reader.GetString(1); // 假设第二列是Name，类型为varchar
-            var age = reader.GetInt32(2); // 假设第三列是Age，可为空
+            var id = reader.GetInt32("id");
+            var name = reader.GetString("name");
+            var age = reader.GetInt32("age");
 
-            Console.WriteLine($"ID: {id}, Name: {name}, Age: {age}");
+            Console.WriteLine($@"ID: {id}, Name: {name}, Age: {age}");
         }
     }
 }