C#检查数据是否已存在

using System;
using System.Data.SqlClient;

public class DatabaseChecker
{
    public bool IsDataExist(string connectionString, string tableName, string columnName, string value)
    {
        bool isExist = false;
        
        using (SqlConnection connection = new SqlConnection(connectionString))
        {
            connection.Open();
            
            string query = $"SELECT COUNT(*) FROM {tableName} WHERE {columnName} = @Value";
            SqlCommand command = new SqlCommand(query, connection);
            command.Parameters.AddWithValue("@Value", value);
            
            int count = (int)command.ExecuteScalar();
            
            if (count > 0)
            {
                isExist = true;
            }
        }
        
        return isExist;
    }
}

// 使用示例
string connectionString = "your_connection_string";
string tableName = "your_table_name";
string columnName = "your_column_name";
string valueToCheck = "your_value";

DatabaseChecker checker = new DatabaseChecker();
bool isExist = checker.IsDataExist(connectionString, tableName, columnName, valueToCheck);

if (isExist)
{
    Console.WriteLine("Data already exists!");
}
else
{
    Console.WriteLine("Data does not exist!");
}