GetAccessToken_ClientSecretCredential.cs

using Azure.Identity;

public async Task<string> GetAccessTokenAsync(string resourceUrl, string tenantId, string clientId, string clientSecret)
{
    var credential = new ClientSecretCredential(tenantId, clientId, clientSecret);

    var accessToken = await credential.GetTokenAsync(new TokenRequestContext(scopes: [resourceUrl + "/.default"]) { });

    return accessToken.Token;
}